Replacing the ferromagnet with ferrimagnet (FiM) in the magnetic tunnel junction (MTJ) allows faster magnetization switching in picoseconds. The operation of a memory cell that consists of the MTJ and a transistor requires reversable magnetization switching. When a constant voltage is applied, we find that the spin-transfer torque can only switch the FiM-MTJ from parallel to antiparallel state. This stems from the small switching window of FiM and the dynamic resistance variation during the magnetization switching. We find the resulting current variation can be suppressed by reducing the magnetoresistance ratio. Furthermore, we demonstrate that the switching window can be expanded by adjusting the amount of Gd in FiM. We predict that the polarity of both switching current (Jc,switch) and oscillation current (Jc,osc) reverses at the angular momentum compensation point but not the magnetization compensation point. This anomalous dynamic behavior is attributed to the different physical nature of magnetization switching and oscillation in FiM, which must be considered when designing FiM-based MRAM.
在磁隧道结（MTJ）中用铁磁体（FiM）取代铁磁体，可以在皮秒级的时间内实现更快的磁化切换。由 MTJ 和晶体管组成的存储单元的运行需要可逆的磁化切换。当施加恒定电压时，我们发现自旋转移力矩只能将 FiM-MTJ 从平行状态切换到反平行状态。这是因为 FiM 的开关窗口较小，而且在磁化切换过程中存在动态电阻变化。我们发现可以通过降低磁阻比来抑制由此产生的电流变化。此外，我们还证明可以通过调整 FiM 中的钆含量来扩大开关窗口。我们预测开关电流（Jc,switch）和振荡电流（Jc,osc）的极性在角动量补偿点会反转，但在磁化补偿点不会。这种反常的动态行为归因于 FiM 中磁化开关和振荡的不同物理特性，在设计基于 FiM 的 MRAM 时必须考虑到这一点。
{"title":"Anomalous switching pattern in the ferrimagnetic memory cell","authors":"Zhuo Xu , Zhengping Yuan , Xue Zhang , Zhengde Xu , Yixiao Qiao , Yumeng Yang , Zhifeng Zhu","doi":"10.1016/j.jmmm.2024.172614","DOIUrl":"10.1016/j.jmmm.2024.172614","url":null,"abstract":"<div><div>Replacing the ferromagnet with ferrimagnet (FiM) in the magnetic tunnel junction (MTJ) allows faster magnetization switching in picoseconds. The operation of a memory cell that consists of the MTJ and a transistor requires reversable magnetization switching. When a constant voltage is applied, we find that the spin-transfer torque can only switch the FiM-MTJ from parallel to antiparallel state. This stems from the small switching window of FiM and the dynamic resistance variation during the magnetization switching. We find the resulting current variation can be suppressed by reducing the magnetoresistance ratio. Furthermore, we demonstrate that the switching window can be expanded by adjusting the amount of Gd in FiM. We predict that the polarity of both switching current (<em>J</em><sub>c,switch</sub>) and oscillation current (<em>J</em><sub>c,osc</sub>) reverses at the angular momentum compensation point but not the magnetization compensation point. This anomalous dynamic behavior is attributed to the different physical nature of magnetization switching and oscillation in FiM, which must be considered when designing FiM-based MRAM.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172614"},"PeriodicalIF":2.5,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-02DOI: 10.1016/j.jmmm.2024.172637
Mohammadmahdi Kamyabi, Seyed Mohammad Sadegh Hosseini
This study experimentally investigates the effects of magnetic field strength, Reynolds number, and nanoparticle concentration on the unsteady heat transfer characteristics of a Fe3O4-water nanofluid. The nanofluid was prepared by dispersing nanoparticles in water at concentrations of 0 %, 0.08% v/v and 0.16% v/v, using a stabilizer to maintain dispersion. A double-pipe system, encased in a copper coil (solenoid), was employed to facilitate heat exchange between tap water and the nanofluid under magnetic field. The solenoid exerts the desired magnetic field. The Taguchi method was utilized for experimental design and analysis. Results indicate that the Reynolds number, magnetic field strength, and nanofluid concentration all enhance the heat transfer rate; however, their effects differ due to distinct mechanisms of action. Analysis of variance reveals that the Reynolds number has the most significant impact although at low Reynolds only. This is while the effects of nanoparticle concentration and magnetic field strength are comparable. The findings suggest that even a magnetic field aligned with the fluid flow can serve as an auxiliary factor to enhance heat transfer in ferrofluids, particularly when increasing nanoparticle concentration is constrained by rising pressure drops and the risk of agglomeration.
{"title":"Magnetic field effects on the thermal performance of Fe3O4 nanofluids in a forced convection system","authors":"Mohammadmahdi Kamyabi, Seyed Mohammad Sadegh Hosseini","doi":"10.1016/j.jmmm.2024.172637","DOIUrl":"10.1016/j.jmmm.2024.172637","url":null,"abstract":"<div><div>This study experimentally investigates the effects of magnetic field strength, Reynolds number, and nanoparticle concentration on the unsteady heat transfer characteristics of a Fe<sub>3</sub>O<sub>4</sub>-water nanofluid. The nanofluid was prepared by dispersing nanoparticles in water at concentrations of 0 %, 0.08% v/v and 0.16% v/v, using a stabilizer to maintain dispersion. A double-pipe system, encased in a copper coil (solenoid), was employed to facilitate heat exchange between tap water and the nanofluid under magnetic field. The solenoid exerts the desired magnetic field. The Taguchi method was utilized for experimental design and analysis. Results indicate that the Reynolds number, magnetic field strength, and nanofluid concentration all enhance the heat transfer rate; however, their effects differ due to distinct mechanisms of action. Analysis of variance reveals that the Reynolds number has the most significant impact although at low Reynolds only. This is while the effects of nanoparticle concentration and magnetic field strength are comparable. The findings suggest that even a magnetic field aligned with the fluid flow can serve as an auxiliary factor to enhance heat transfer in ferrofluids, particularly when increasing nanoparticle concentration is constrained by rising pressure drops and the risk of agglomeration.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172637"},"PeriodicalIF":2.5,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.jmmm.2024.172635
M. Wilczyński, K. Zberecki, M. Wierzbicki
The charge current flowing through the triple junction composed of ferromagnetic external electrodes and inner layers of different thickness separated by three non-magnetic barriers is analysed in four colinear magnetic configurations. The thickness of the inner layers and the bias voltage can be set in such a way that the junction can act as a tunnel diode with current flowing effectively in one specific direction. The diode properties of the junction can be adjusted by a change of relative orientation of magnetic moments in the inner layers and electrodes; especially the junction can act as a diode in only one magnetic configuration. Magnetic configuration switching can also reverse the direction of the flow of tunnel current.
{"title":"Effective spin filter and diode based on triple magnetic junction","authors":"M. Wilczyński, K. Zberecki, M. Wierzbicki","doi":"10.1016/j.jmmm.2024.172635","DOIUrl":"10.1016/j.jmmm.2024.172635","url":null,"abstract":"<div><div>The charge current flowing through the triple junction composed of ferromagnetic external electrodes and inner layers of different thickness separated by three non-magnetic barriers is analysed in four colinear magnetic configurations. The thickness of the inner layers and the bias voltage can be set in such a way that the junction can act as a tunnel diode with current flowing effectively in one specific direction. The diode properties of the junction can be adjusted by a change of relative orientation of magnetic moments in the inner layers and electrodes; especially the junction can act as a diode in only one magnetic configuration. Magnetic configuration switching can also reverse the direction of the flow of tunnel current.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172635"},"PeriodicalIF":2.5,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.jmmm.2024.172632
Zhihong Hao , Xiaojuan Wang , Yao Liu , Taosheng Zhong , Lina Zhang , Changwang Yuan , Licheng Xiao , Hui Liu , Juguo Zhang
The development of high-performance magnetocaloric materials has garnered significant attention due to their potential applications in magnetic refrigeration technology. Element doping has emerged as a crucial strategy for enhancing the magnetocaloric properties of these materials. In this study, we present the enhanced magnetocaloric effect in the HoCo0.8Fe0.2C compound through Fe doping. The Fe doping not only induces a ferromagnetic transition but also significantly improves the magnetocaloric performance of the compound. Under a magnetic field change from 0 to 7 T, the HoCo0.8Fe0.2C compound exhibits a maximum magnetic entropy change () of 20.5 J/kg K and a refrigerant capacity (RC) of 573.3 J/kg. Additionally, this compound undergoes a spin reorientation transition at 11 K and a ferromagnetic to paramagnetic transition at 18 K. These transitions are critical to understanding the magnetocaloric behavior of the material. The results highlight the potential of Fe-doped HoCo0.8Fe0.2C as an efficient magnetocaloric material, contributing to the advancement of magnetic refrigeration technology at low temperatures. Our study underscores the impact of element doping on the magnetic and magnetocaloric properties of intermetallic compounds.
由于高性能磁致冷材料在磁制冷技术中的潜在应用，它们的开发备受关注。元素掺杂已成为增强这些材料磁致性的重要策略。在本研究中，我们介绍了通过掺杂铁元素增强 HoCo0.8Fe0.2C 化合物的磁致效应。铁的掺杂不仅诱导了铁磁转变，还显著提高了化合物的磁致性能。在 0 到 7 T 的磁场变化下，HoCo0.8Fe0.2C 化合物的最大磁熵变（-ΔSMmax）为 20.5 J/kg K，制冷剂容量（RC）为 573.3 J/kg。此外，这种化合物在 11 K 时发生了自旋重新定向转变，在 18 K 时发生了从铁磁性到顺磁性的转变。研究结果凸显了掺铁 HoCo0.8Fe0.2C 作为高效磁致变材料的潜力，有助于推动低温磁制冷技术的发展。我们的研究强调了元素掺杂对金属间化合物磁性和磁致性的影响。
{"title":"Enhanced low field magnetocaloric effect through Fe doping induced ferromagnetic transition in HoCo0.8Fe0.2C compound","authors":"Zhihong Hao , Xiaojuan Wang , Yao Liu , Taosheng Zhong , Lina Zhang , Changwang Yuan , Licheng Xiao , Hui Liu , Juguo Zhang","doi":"10.1016/j.jmmm.2024.172632","DOIUrl":"10.1016/j.jmmm.2024.172632","url":null,"abstract":"<div><div>The development of high-performance magnetocaloric materials has garnered significant attention due to their potential applications in magnetic refrigeration technology. Element doping has emerged as a crucial strategy for enhancing the magnetocaloric properties of these materials. In this study, we present the enhanced magnetocaloric effect in the HoCo<sub>0.8</sub>Fe<sub>0.2</sub>C compound through Fe doping. The Fe doping not only induces a ferromagnetic transition but also significantly improves the magnetocaloric performance of the compound. Under a magnetic field change from 0 to 7 T, the HoCo<sub>0.8</sub>Fe<sub>0.2</sub>C compound exhibits a maximum magnetic entropy change (<span><math><msubsup><mrow><mo>-</mo><mi>Δ</mi><mi>S</mi></mrow><mrow><mi>M</mi></mrow><mrow><mi>max</mi></mrow></msubsup></math></span>) of 20.5 J/kg K and a refrigerant capacity (RC) of 573.3 J/kg. Additionally, this compound undergoes a spin reorientation transition at 11 K and a ferromagnetic to paramagnetic transition at 18 K. These transitions are critical to understanding the magnetocaloric behavior of the material. The results highlight the potential of Fe-doped HoCo<sub>0.8</sub>Fe<sub>0.2</sub>C as an efficient magnetocaloric material, contributing to the advancement of magnetic refrigeration technology at low temperatures. Our study underscores the impact of element doping on the magnetic and magnetocaloric properties of intermetallic compounds.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172632"},"PeriodicalIF":2.5,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.jmmm.2024.172617
Ashiwini Balodhi, Min Gyu Kim
Magnetization and heat capacity () measurements were performed on blade-shaped single crystals of LiCuO, a one-dimensional spin-chain compound synthesized via the flux method. The magnetization and heat capacity measurements confirm a long-range antiferromagnetic transition at = 9.3 K. The magnetic susceptibility, with magnetic field applied parallel () and perpendicular () to the spin chain direction (crystallographic -axis) is reported. measurements reveal anisotropic behavior, with in the temperature range K, with a ratio of = 1.15 at 300 K and with at K, with a ratio of = 0.86 at 2 K. Unlike the previous studies reporting ferromagnetic components at low temperatures, we report the absence of a ferromagnetic ordering at low temperatures.
对通过磁通量法合成的一维自旋链化合物 Li2CuO2 的叶片形单晶进行了磁化和热容（Cp）测量。磁化和热容测量证实了 TN = 9.3 K 时的长程反铁磁转变。报告了磁感应强度 χ 在与自旋链方向（晶体学 b 轴）平行（χ∥b）和垂直（χ⊥b）磁场下的变化情况。χ(T)测量显示了各向异性行为，在 TN<T<350 K 温度范围内，χ⊥b >χ∥b 的比率为 χ⊥/χ∥ = 1.15 ，在 300 K 时为 χ⊥b <χ∥b ，在 T=2 K 时为 χ⊥/χ∥ = 0.与之前报告低温下铁磁成分的研究不同，我们报告在低温下没有铁磁有序。
{"title":"Magnetic susceptibility and heat capacity of a quasi-spin chain compound, Li2CuO2","authors":"Ashiwini Balodhi, Min Gyu Kim","doi":"10.1016/j.jmmm.2024.172617","DOIUrl":"10.1016/j.jmmm.2024.172617","url":null,"abstract":"<div><div>Magnetization and heat capacity (<span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>) measurements were performed on blade-shaped single crystals of Li<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>CuO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>, a one-dimensional spin-chain compound synthesized via the flux method. The magnetization and heat capacity measurements confirm a long-range antiferromagnetic transition at <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>N</mi></mrow></msub></math></span> = 9.3 K. The magnetic susceptibility, <span><math><mi>χ</mi></math></span> with magnetic field applied parallel (<span><math><msub><mrow><mi>χ</mi></mrow><mrow><mo>∥</mo><mi>b</mi></mrow></msub></math></span>) and perpendicular (<span><math><msub><mrow><mi>χ</mi></mrow><mrow><mo>⊥</mo><mi>b</mi></mrow></msub></math></span>) to the spin chain direction (crystallographic <span><math><mi>b</mi></math></span>-axis) is reported. <span><math><mrow><mi>χ</mi><mrow><mo>(</mo><mi>T</mi><mo>)</mo></mrow></mrow></math></span> measurements reveal anisotropic behavior, with <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mo>⊥</mo><mi>b</mi></mrow></msub></math></span> <span><math><mrow><mo>></mo><msub><mrow><mi>χ</mi></mrow><mrow><mo>∥</mo><mi>b</mi></mrow></msub></mrow></math></span> in the temperature range <span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>N</mi></mrow></msub><mo><</mo><mi>T</mi><mo><</mo><mn>350</mn></mrow></math></span> K, with a ratio of <span><math><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mo>⊥</mo></mrow></msub><mo>/</mo><msub><mrow><mi>χ</mi></mrow><mrow><mo>∥</mo></mrow></msub></mrow></math></span> = 1.15 at 300 K and with <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mo>⊥</mo><mi>b</mi></mrow></msub></math></span> <span><math><mrow><mo><</mo><msub><mrow><mi>χ</mi></mrow><mrow><mo>∥</mo><mi>b</mi></mrow></msub></mrow></math></span> at <span><math><mrow><mi>T</mi><mo>=</mo><mn>2</mn></mrow></math></span> K, with a ratio of <span><math><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mo>⊥</mo></mrow></msub><mo>/</mo><msub><mrow><mi>χ</mi></mrow><mrow><mo>∥</mo></mrow></msub></mrow></math></span> = 0.86 at 2 K. Unlike the previous studies reporting ferromagnetic components at low temperatures, we report the absence of a ferromagnetic ordering at low temperatures.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172617"},"PeriodicalIF":2.5,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-29DOI: 10.1016/j.jmmm.2024.172629
Lakhdar Benahmedi, Anissa Besbes, Radouan Djelti
In this study, we comprehensively investigate the structural, electronic, magnetic, elastic, and thermal properties of the double perovskite Ba2InOsO6 using density functional theory (DFT). Our results show that the ferromagnetic phase is the most stable, with the net magnetic moment primarily arising from the Os atom. The half-metallic behavior exhibited by Ba2InOsO6, characterized by a band gap of 3.62 eV in the TB-mBJ + U approximation, decreases upon the inclusion of spin–orbit coupling (SOC). This half-metallic property, coupled with the stability of the ferromagnetic phase, makes Ba2InOsO6 particularly suitable for spintronic applications, as it can facilitate efficient spin injection and transport. Elasticity analysis indicates moderate brittleness, while thermoelectric properties, calculated using the Boltzmann transport model, reveal n-type conductivity and notable thermopower, suggesting potential for thermoelectric applications. This work provides a solid foundation for future experimental studies and potential applications in advanced technologies.
在这项研究中，我们利用密度泛函理论（DFT）全面研究了双包晶石 Ba2InOsO6 的结构、电子、磁性、弹性和热特性。研究结果表明，铁磁相最为稳定，其净磁矩主要来自 Os 原子。在 TB-mBJ + U 近似条件下，Ba2InOsO6 的带隙为 3.62 eV，当加入自旋轨道耦合（SOC）时，Ba2InOsO6 表现出的半金属特性会减弱。这种半金属特性加上铁磁相的稳定性，使 Ba2InOsO6 特别适用于自旋电子应用，因为它能促进有效的自旋注入和传输。弹性分析表明它具有适度的脆性，而使用玻尔兹曼输运模型计算得出的热电性能则显示出 n 型导电性和显著的热功率，这表明它具有热电应用的潜力。这项工作为未来的实验研究和先进技术的潜在应用奠定了坚实的基础。
{"title":"Structural, magnetic, elastic, and thermoelectric properties of Ba2InOsO6 double perovskite in the cubic phase: A DFT + U study with spin-orbit-coupling","authors":"Lakhdar Benahmedi, Anissa Besbes, Radouan Djelti","doi":"10.1016/j.jmmm.2024.172629","DOIUrl":"10.1016/j.jmmm.2024.172629","url":null,"abstract":"<div><div>In this study, we comprehensively investigate the structural, electronic, magnetic, elastic, and thermal properties of the double perovskite Ba<sub>2</sub>InOsO<sub>6</sub> using density functional theory (DFT). Our results show that the ferromagnetic phase is the most stable, with the net magnetic moment primarily arising from the Os atom. The half-metallic behavior exhibited by Ba<sub>2</sub>InOsO<sub>6,</sub> characterized by a band gap of 3.62 eV in the TB-mBJ + U approximation, decreases upon the inclusion of spin–orbit coupling (SOC). This half-metallic property, coupled with the stability of the ferromagnetic phase, makes Ba<sub>2</sub>InOsO<sub>6</sub> particularly suitable for spintronic applications, as it can facilitate efficient spin injection and transport. Elasticity analysis indicates moderate brittleness, while thermoelectric properties, calculated using the Boltzmann transport model, reveal n-type conductivity and notable thermopower, suggesting potential for thermoelectric applications. This work provides a solid foundation for future experimental studies and potential applications in advanced technologies.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172629"},"PeriodicalIF":2.5,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-28DOI: 10.1016/j.jmmm.2024.172615
Jiawei Liu , Decai Li , Jiahao Dong , Sijia Liu , Jingcheng Cai
Magnetic fluid seal (MFS) is one of the most mature applications of magnetic fluid (MF) and is widely used in numerous fields. But challenges arise in maintaining the volume of MF within the sealing gap, particularly under conditions of elevated seal pressure, high rotational speeds, and long-term usage. Injecting MF in multi-stage MFS post-installation poses a notable challenge. The conventional approach of injecting the entire optimal volume into pole teeth faces difficulties, as a portion of the MF tends to adhere to the surface of shaft and pole shoes during installation due to the uneven magnetic field. This study aimed to explore MF injection and devise a method for precisely controlling the MF volume in the sealing gap. To achieve this, a novel concept of multi-stage MFS with larger sealing gaps in specific stages was introduced. The injection and movement of MF were scrutinized through a combination of Computational Fluid Dynamics (CFD) simulations and experimental investigations. The findings from both CFD and experiments unequivocally establish the feasibility of injecting MF in multi-stage MFS. Effective injection is achieved when the inlet pressure increment is maintained below 20 kPa each time. Furthermore, experimental results highlight that the sealing capacity achieved through the injection method surpasses that of the common injection method, particularly for optimal volume MFS.
{"title":"Theory analysis and experimental study on magnetic fluid injection of multi-stage magnetic fluid seal","authors":"Jiawei Liu , Decai Li , Jiahao Dong , Sijia Liu , Jingcheng Cai","doi":"10.1016/j.jmmm.2024.172615","DOIUrl":"10.1016/j.jmmm.2024.172615","url":null,"abstract":"<div><div>Magnetic fluid seal (MFS) is one of the most mature applications of magnetic fluid (MF) and is widely used in numerous fields. But challenges arise in maintaining the volume of MF within the sealing gap, particularly under conditions of elevated seal pressure, high rotational speeds, and long-term usage. Injecting MF in multi-stage MFS post-installation poses a notable challenge. The conventional approach of injecting the entire optimal volume into pole teeth faces difficulties, as a portion of the MF tends to adhere to the surface of shaft and pole shoes during installation due to the uneven magnetic field. This study aimed to explore MF injection and devise a method for precisely controlling the MF volume in the sealing gap. To achieve this, a novel concept of multi-stage MFS with larger sealing gaps in specific stages was introduced. The injection and movement of MF were scrutinized through a combination of Computational Fluid Dynamics (CFD) simulations and experimental investigations. The findings from both CFD and experiments unequivocally establish the feasibility of injecting MF in multi-stage MFS. Effective injection is achieved when the inlet pressure increment is maintained below 20 kPa each time. Furthermore, experimental results highlight that the sealing capacity achieved through the injection method surpasses that of the common injection method, particularly for optimal volume MFS.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172615"},"PeriodicalIF":2.5,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-28DOI: 10.1016/j.jmmm.2024.172616
Ali Mahmoudi, Majid Mesbah
This paper addresses the persistent issue of black powder—solid suspended particles in natural gas streams—that can cause significant damage to gas industry equipment. Despite existing purification processes, black powder remains a challenge due to the limitations of conventional particle removal techniques. To overcome these drawbacks, this study proposes a novel magnetic filter that offers superior efficiency in capturing even submicron particles, significantly reducing maintenance costs and addressing the longstanding problem of black powder accumulation. The properties of black powder and existing separation methods in the natural gas industry are explored, and the performance of the magnetic filter is evaluated through comprehensive numerical analysis using the Discrete Phase Model (DPM). Results demonstrate the filter’s capability to efficiently capture particles as small as 5 µm, with an impressive removal efficiency of 92% for particles as small as 1 µm. This study provides valuable insights into addressing the persistent issue of black powder in natural gas streams and presents a promising solution for its efficient removal, ensuring the long-term integrity and durability of equipment used in natural gas transmission systems.
{"title":"Numerical assessment of black powder removal from natural gas using magnetophoresis","authors":"Ali Mahmoudi, Majid Mesbah","doi":"10.1016/j.jmmm.2024.172616","DOIUrl":"10.1016/j.jmmm.2024.172616","url":null,"abstract":"<div><div>This paper addresses the persistent issue of black powder—solid suspended particles in natural gas streams—that can cause significant damage to gas industry equipment. Despite existing purification processes, black powder remains a challenge due to the limitations of conventional particle removal techniques. To overcome these drawbacks, this study proposes a novel magnetic filter that offers superior efficiency in capturing even submicron particles, significantly reducing maintenance costs and addressing the longstanding problem of black powder accumulation. The properties of black powder and existing separation methods in the natural gas industry are explored, and the performance of the magnetic filter is evaluated through comprehensive numerical analysis using the Discrete Phase Model (DPM). Results demonstrate the filter’s capability to efficiently capture particles as small as 5 µm, with an impressive removal efficiency of 92% for particles as small as 1 µm. This study provides valuable insights into addressing the persistent issue of black powder in natural gas streams and presents a promising solution for its efficient removal, ensuring the long-term integrity and durability of equipment used in natural gas transmission systems.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172616"},"PeriodicalIF":2.5,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gd–Al–Co-doped BaFe12−3x(GdAlCo)xO19 (x = 0, 0.1, 0.2, 0.3, 0.4) was synthesized via the hydrothermal method. We performed comprehensive characterization using XRD, SEM, BET, VSM, XPS, and VNA techniques to explore the impact of substituting magnetic Co2+, Gd3+, and nonmagnetic Al3+ for Fe3+ on the morphology, specific surface area, magnetic, and microwave absorption (MWA) properties of BaFe12−3x(GdAlCo)xO19. Investigating the MWA properties of BaFe12−3x(GdAlCo)xO19 in the 2–18 GHz range, we find that all doped samples demonstrate excellent MWA characteristics. The sample BaFe11.1(GdAlCo)0.3O19 achieves a minimum reflection loss (RLmin) of − 48.13 dB at a thickness of 2.07 mm, indicating an absorption of over 99 % of incident microwaves. The effective absorption bandwidth (EAB) for all four groups of doped samples exceeds 5.98 GHz. Notably, the x = 0.1 samples reach an EAB of 9.15 GHz at only 2.0 mm thickness, covering most of the X-band and the entire Ku band. Gd-Al-Co co doping of BaFe12O19 not only improves its reflection loss ability, but also increases its absorption bandwidth. Improved the drawbacks of narrow bandwidth and poor loss capability in BaFe12O19. Consequently, BaFe12−3x(GdAlCo)xO19 material shows significant potential for practical applications.
{"title":"Broadband microwave absorption and electromagnetic properties of Gd–Al–Co-doped M−type barium hexaferrite in 2–18 GHz range","authors":"Weihua Liao, Kai Huang, Wenwen Xu, Jiangying Yu, Ping Li, Jinrong Xu","doi":"10.1016/j.jmmm.2024.172609","DOIUrl":"10.1016/j.jmmm.2024.172609","url":null,"abstract":"<div><div>Gd–Al–Co-doped BaFe<sub>12−3x</sub>(GdAlCo)<sub>x</sub>O<sub>19</sub> (x = 0, 0.1, 0.2, 0.3, 0.4) was synthesized via the hydrothermal method. We performed comprehensive characterization using XRD, SEM, BET, VSM, XPS, and VNA techniques to explore the impact of substituting magnetic Co<sup>2+</sup>, Gd<sup>3+</sup>, and nonmagnetic Al<sup>3+</sup> for Fe<sup>3+</sup> on the morphology, specific surface area, magnetic, and microwave absorption (MWA) properties of BaFe<sub>12−3x</sub>(GdAlCo)<sub>x</sub>O<sub>19</sub>. Investigating the MWA properties of BaFe<sub>12−3x</sub>(GdAlCo)<sub>x</sub>O<sub>19</sub> in the 2–18 GHz range, we find that all doped samples demonstrate excellent MWA characteristics. The sample BaFe<sub>11.1</sub>(GdAlCo)<sub>0.3</sub>O<sub>19</sub> achieves a minimum reflection loss (RL<sub>min</sub>) of − 48.13 dB at a thickness of 2.07 mm, indicating an absorption of over 99 % of incident microwaves. The effective absorption bandwidth (EAB) for all four groups of doped samples exceeds 5.98 GHz. Notably, the x = 0.1 samples reach an EAB of 9.15 GHz at only 2.0 mm thickness, covering most of the X-band and the entire Ku band. Gd-Al-Co co doping of BaFe<sub>12</sub>O<sub>19</sub> not only improves its reflection loss ability, but also increases its absorption bandwidth. Improved the drawbacks of narrow bandwidth and poor loss capability in BaFe<sub>12</sub>O<sub>19</sub>. Consequently, BaFe<sub>12−3x</sub>(GdAlCo)<sub>x</sub>O<sub>19</sub> material shows significant potential for practical applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172609"},"PeriodicalIF":2.5,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-24DOI: 10.1016/j.jmmm.2024.172608
Babu Ram Sankhi , Erwan Peigney , Hayden Brown , Pius Suh , Carlos Rojas-Dotti , José Martínez-Lillo , Pawan Tyagi
The integration of single-molecule magnets (SMMs) into magnetic tunnel junctions (MTJs) offers significant potential for advancing molecular spintronics, particularly for next-generation memory devices, quantum computing, and energy storage technologies such as solar cells. In this study, we present the first demonstration of SMM-induced spin-dependent properties in an antiferromagnet-based MTJ molecular spintronic device (MTJMSD). We engineered cross-junction-shaped devices comprising FeMn/AlOx/NiFe MTJs. The AlOx barrier thickness where the exposed junction edges meet was comparable to the SMM length, facilitating the incorporation of SMM molecules as spin channels for spin-dependent transport. The SMM channels enabled long-range magnetic moment ordering around molecular junctions, which were precisely engineered via fabrication processes. The SMM, composed of a [Mn6(μ3-O)2(H2N-sao)6(6-atha)2(EtOH)6] (H2N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate) complex, featured thioester groups at the ends that upon hydrolysis they form bonds with the magnetic electrodes. SMM-treated junctions demonstrated a significant current enhancement, reaching up to 7 μA at an input voltage of 60 mV. Furthermore, SMM-doped junctions exhibited current stabilization in the μA range at lower temperatures, whereas the bare electrodes showed current suppression to the picoampere range. Magnetization measurements conducted at 55 K and 300 K on pillar-shaped devices revealed a reduction in magnetic moment at low temperatures. Additionally, Kelvin probe atomic force microscopy (KPAFM) measurements confirmed that SMM integration transformed the electronic properties over long ranges.These findings are attributed to the spin channels formed between magnetic metal electrodes, which enhance spin polarization at each magnetic electrode. Our research highlights the potential of using antiferromagnetic materials, characterized by minimal stray fields and zero net magnetization, to transform MTJMSD devices.
{"title":"Single-molecule Magnets (SMM) spin channels connecting FeMn antiferromagnet and NiFe ferromagnetic electrodes of a tunnel junction","authors":"Babu Ram Sankhi , Erwan Peigney , Hayden Brown , Pius Suh , Carlos Rojas-Dotti , José Martínez-Lillo , Pawan Tyagi","doi":"10.1016/j.jmmm.2024.172608","DOIUrl":"10.1016/j.jmmm.2024.172608","url":null,"abstract":"<div><div>The integration of single-molecule magnets (SMMs) into magnetic tunnel junctions (MTJs) offers significant potential for advancing molecular spintronics, particularly for next-generation memory devices, quantum computing, and energy storage technologies such as solar cells. In this study, we present the first demonstration of SMM-induced spin-dependent properties in an antiferromagnet-based MTJ molecular spintronic device (MTJMSD). We engineered cross-junction-shaped devices comprising FeMn/AlO<sub>x</sub>/NiFe MTJs. The AlO<sub>x</sub> barrier thickness where the exposed junction edges meet was comparable to the SMM length, facilitating the incorporation of SMM molecules as spin channels for spin-dependent transport. The SMM channels enabled long-range magnetic moment ordering around molecular junctions, which were precisely engineered via fabrication processes. The SMM, composed of a [Mn<sub>6</sub>(μ<sub>3</sub>-O)<sub>2</sub>(H<sub>2</sub>N-sao)<sub>6</sub>(6-atha)<sub>2</sub>(EtOH)<sub>6</sub>] (H<sub>2</sub>N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate) complex, featured thioester groups at the ends that upon hydrolysis they form bonds with the magnetic electrodes. SMM-treated junctions demonstrated a significant current enhancement, reaching up to 7 μA at an input voltage of 60 mV. Furthermore, SMM-doped junctions exhibited current stabilization in the μA range at lower temperatures, whereas the bare electrodes showed current suppression to the picoampere range. Magnetization measurements conducted at 55 K and 300 K on pillar-shaped devices revealed a reduction in magnetic moment at low temperatures. Additionally, Kelvin probe atomic force microscopy (KPAFM) measurements confirmed that SMM integration transformed the electronic properties over long ranges.These findings are attributed to the spin channels formed between magnetic metal electrodes, which enhance spin polarization at each magnetic electrode. Our research highlights the potential of using antiferromagnetic materials, characterized by minimal stray fields and zero net magnetization, to transform MTJMSD devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172608"},"PeriodicalIF":2.5,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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