Pub Date : 2024-11-07DOI: 10.1016/j.jmmm.2024.172631
Resta A. Susilo , J.M. Cadogan , W.D. Hutchison , M. Avdeev , S.J. Campbell
We have investigated the effects of Lu substitution on the magnetic behaviour and ordering of (HoLu)2Fe2Si2C ( = 0.32 and 0.46) by high-resolution neutron powder diffraction, magnetisation and specific heat over the temperature range 2 to 300 K. Our study has established that the antiferromagnetic (AFM) state is weakened upon Lu substitution and that the Néel temperature T shifts towards lower temperature with increasing Lu content. The replacement of the magnetic Ho ion by the non-magnetic Lu ion of smaller atomic radius, leads to a modification of the crystal field levels, as indicated by the specific heat measurements. Neutron diffraction data analysis reveals that the magnetic structure of undoped Ho2Fe2Si2C, which exhibits a commensurate, antiferromagnetic ordering of the Ho sublattice along the -axis with a propagation vector k = [0, 0, ], is maintained in the Lu-doped (HoLu)2Fe2Si2C compounds.
我们通过高分辨率中子粉末衍射、磁化和比热研究了 Lu 取代对 (Ho1-xLux)2Fe2Si2C （x = 0.32 和 0.46）在 2 至 300 K 温度范围内的磁性和有序性的影响。用原子半径较小的非磁性 Lu3+ 离子取代磁性 Ho3+ 离子会导致晶体场水平的改变，比热测量结果也表明了这一点。中子衍射数据分析显示，未掺杂的 Ho2Fe2Si2C 的磁性结构在掺杂 Lu 的 (Ho1-xLux)2Fe2Si2C 化合物中保持不变，这种磁性结构显示了 Ho 亚晶格沿 b 轴的相称反铁磁有序性，传播矢量 k = [0, 0, 12]。
{"title":"Effects of Lu-doping on the magnetic behaviour and ordering of (Ho1−xLux)2Fe2Si2C","authors":"Resta A. Susilo , J.M. Cadogan , W.D. Hutchison , M. Avdeev , S.J. Campbell","doi":"10.1016/j.jmmm.2024.172631","DOIUrl":"10.1016/j.jmmm.2024.172631","url":null,"abstract":"<div><div>We have investigated the effects of Lu substitution on the magnetic behaviour and ordering of (Ho<span><math><msub><mrow></mrow><mrow><mn>1</mn><mo>−</mo><mi>x</mi></mrow></msub></math></span>Lu<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span>)<sub>2</sub>Fe<sub>2</sub>Si<sub>2</sub>C (<span><math><mi>x</mi></math></span> = 0.32 and 0.46) by high-resolution neutron powder diffraction, magnetisation and specific heat over the temperature range 2 to 300 K. Our study has established that the antiferromagnetic (AFM) state is weakened upon Lu substitution and that the Néel temperature T<span><math><msub><mrow></mrow><mrow><mi>N</mi></mrow></msub></math></span> shifts towards lower temperature with increasing Lu content. The replacement of the magnetic Ho<span><math><msup><mrow></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math></span> ion by the non-magnetic Lu<span><math><msup><mrow></mrow><mrow><mn>3</mn><mo>+</mo></mrow></msup></math></span> ion of smaller atomic radius, leads to a modification of the crystal field levels, as indicated by the specific heat measurements. Neutron diffraction data analysis reveals that the magnetic structure of undoped Ho<sub>2</sub>Fe<sub>2</sub>Si<sub>2</sub>C, which exhibits a commensurate, antiferromagnetic ordering of the Ho sublattice along the <span><math><mi>b</mi></math></span>-axis with a propagation vector <strong>k</strong> = [0, 0, <span><math><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac></math></span>], is maintained in the Lu-doped (Ho<span><math><msub><mrow></mrow><mrow><mn>1</mn><mo>−</mo><mi>x</mi></mrow></msub></math></span>Lu<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span>)<sub>2</sub>Fe<sub>2</sub>Si<sub>2</sub>C compounds.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172631"},"PeriodicalIF":2.5,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660797","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 : 2024-11-07DOI: 10.1016/j.jmmm.2024.172634
N.B. Melnikov , A.S. Gulenko , B.I. Reser
We study paramagnetic characteristics of ferromagnetic metals near the Curie temperature using the dynamic spin fluctuation theory. In contrast with most first-principles calculations, our results for the uniform paramagnetic susceptibility show a clear deviation from the Curie–Weiss law. We demonstrate that the susceptibility and correlation radius have the power-law behavior at temperatures up to 1.1–1.15 , which gives an estimate for the region of critical temperatures in metals. Our theoretical critical exponents for Fe, Co, and Ni are in reasonable agreement with the low-field susceptibility measurements and neutron scattering experiments.
{"title":"Paramagnetic susceptibility and spin correlation function of ferromagnetic metals in the critical region","authors":"N.B. Melnikov , A.S. Gulenko , B.I. Reser","doi":"10.1016/j.jmmm.2024.172634","DOIUrl":"10.1016/j.jmmm.2024.172634","url":null,"abstract":"<div><div>We study paramagnetic characteristics of ferromagnetic metals near the Curie temperature <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>C</mi></mrow></msub></math></span> using the dynamic spin fluctuation theory. In contrast with most first-principles calculations, our results for the uniform paramagnetic susceptibility show a clear deviation from the Curie–Weiss law. We demonstrate that the susceptibility and correlation radius have the power-law behavior at temperatures up to 1.1–1.15<!--> <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>C</mi></mrow></msub></math></span>, which gives an estimate for the region of critical temperatures in metals. Our theoretical critical exponents for Fe, Co, and Ni are in reasonable agreement with the low-field susceptibility measurements and neutron scattering experiments.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172634"},"PeriodicalIF":2.5,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660796","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}
In this work, a theoretical model for a periodic bigyrotropic left-handed medium, which is a ferromagnetic semiconductor, is developed. The presence of periodicity in such a structure leads to the formation of Bragg band gaps in the spectrum of propagating waves, both in the microwave and terahertz ranges. Band gaps in the microwave range are formed in the frequency region with double negative effective parameters of the medium. The band gaps density decreases with increasing frequency in the microwave range and increases in the terahertz range.
{"title":"Bragg resonances in left-handed bigyrotropic media based on periodic ferromagnetic semiconductor","authors":"M.A. Morozova , O.V. Matveev , S.V. Grishin , A.V. Bogomolova , S.A. Nikitov","doi":"10.1016/j.jmmm.2024.172630","DOIUrl":"10.1016/j.jmmm.2024.172630","url":null,"abstract":"<div><div>In this work, a theoretical model for a periodic bigyrotropic left-handed medium, which is a ferromagnetic semiconductor, is developed. The presence of periodicity in such a structure leads to the formation of Bragg band gaps in the spectrum of propagating waves, both in the microwave and terahertz ranges. Band gaps in the microwave range are formed in the frequency region with double negative effective parameters of the medium. The band gaps density decreases with increasing frequency in the microwave range and increases in the terahertz range.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172630"},"PeriodicalIF":2.5,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660159","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 : 2024-11-06DOI: 10.1016/j.jmmm.2024.172610
Sukanya Ghosh , Nataša Stojić , Nadia Binggeli
The newly discovered two-dimensional (2D) magnetic semiconductors such as CrI have triggered a surge of interest stemming from their exotic spin-dependent properties and potential applications in spintronics and magneto-optoelectronics. Using first-principle density-functional-theory calculations, we investigate the properties of the spin-polarization texture in momentum space in the prototype 2D centrosymmetric ferromagnetic (FM) bilayer of CrI with perpendicular magnetization, with a goal of identifying general features due to interlayer interaction and their microscopic origins in 2D centrosymmetric FM materials. The FM CrI bilayer displays a rich in-plane spin texture in its highest valence bands. We show the existence of two distinct spin canting effects induced by the coupling of the two FM layers in establishing the in-plane spin texture. The first effect is generated by the mirror-related chirality of the layer stacking and the spin–orbit-polarized nature of the valence states, and yields the same canting on both layers. The second effect is a Rashba-related effect, which in a centrosymmetric ferromagnet induces in a single electronic state two opposite spin-canted components on the two layers, resulting in a notable frustration effect on the energy of the bonding states. Finally, we show that the above effects can be effectively used to manipulate the spin texture via compressive vertical strain, which induces in the FM CrI bilayer valence-band-edge states with canted spins.
新发现的二维（2D）磁性半导体（如 CrI3）因其奇异的自旋相关特性以及在自旋电子学和磁光电子学中的潜在应用而引发了人们的浓厚兴趣。我们利用第一原理密度泛函理论计算，研究了具有垂直磁化的 CrI3 二维中心对称铁磁（FM）双层原型在动量空间中的自旋极化纹理特性，目的是确定二维中心对称 FM 材料中由于层间相互作用而产生的一般特征及其微观起源。调频 CrI3 双层材料的最高价带显示出丰富的面内自旋纹理。我们展示了在建立面内自旋纹理的过程中，两个调频层的耦合诱发了两种不同的自旋悬臂效应。第一种效应由层堆叠的镜像相关手性和价态的自旋轨道极化性质产生，并在两层上产生相同的悬臂效应。第二种效应是与拉什巴效应相关的效应，在中心对称铁磁体中，这种效应会在单个电子态中诱导两层上两个相反的自旋倾斜成分，从而对成键态的能量产生显著的挫折效应。最后，我们展示了上述效应可有效用于通过压缩垂直应变操纵自旋纹理，从而在调频 CrI3 双层中诱导出具有悬臂自旋的价带边状态。
{"title":"Chirality- and Rashba- related effects in the spin texture of a two-dimensional centrosymmetric ferromagnet: The case of the CrI3 bilayer","authors":"Sukanya Ghosh , Nataša Stojić , Nadia Binggeli","doi":"10.1016/j.jmmm.2024.172610","DOIUrl":"10.1016/j.jmmm.2024.172610","url":null,"abstract":"<div><div>The newly discovered two-dimensional (2D) magnetic semiconductors such as CrI<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> have triggered a surge of interest stemming from their exotic spin-dependent properties and potential applications in spintronics and magneto-optoelectronics. Using first-principle density-functional-theory calculations, we investigate the properties of the spin-polarization texture in momentum space in the prototype 2D centrosymmetric ferromagnetic (FM) bilayer of CrI<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> with perpendicular magnetization, with a goal of identifying general features due to interlayer interaction and their microscopic origins in 2D centrosymmetric FM materials. The FM CrI<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> bilayer displays a rich in-plane spin texture in its highest valence bands. We show the existence of two distinct spin canting effects induced by the coupling of the two FM layers in establishing the in-plane spin texture. The first effect is generated by the mirror-related chirality of the layer stacking and the spin–orbit-polarized nature of the valence states, and yields the same canting on both layers. The second effect is a Rashba-related effect, which in a centrosymmetric ferromagnet induces in a single electronic state two opposite spin-canted components on the two layers, resulting in a notable frustration effect on the energy of the bonding states. Finally, we show that the above effects can be effectively used to manipulate the spin texture via compressive vertical strain, which induces in the FM CrI<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> bilayer valence-band-edge states with canted spins.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172610"},"PeriodicalIF":2.5,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660790","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 : 2024-11-06DOI: 10.1016/j.jmmm.2024.172645
Mehdi Fadaei, Sahand Majidi, Hadi Shoeibi
Micro-magnetofluidics, the study of fluid behavior under magnetic fields in microscale systems, is vital for applications like drug delivery, chemical synthesis, and lab-on-a-chip technologies. Controlling droplet size and formation frequency in these systems is challenging due to the complex interplay of magnetic forces and fluid dynamics. This study introduces a novel approach to control droplet generation in a co-flowing microchannel under a non-uniform magnetic field generated by an electric current loop. Critical parameters such as electric current intensity, continuous phase flow rate, and current loop position are systematically examined for their impact on droplet behavior. The results highlight the unique influence of the magnetic field configuration, specifically the electric current loop, in inducing a transition from dripping to jetting flow patterns with increasing current intensity, leading to larger droplets and reduced generation frequency. Additionally, a distinct behavior of droplet coalescence near the current loop, followed by re-separation, is observed when the loop is positioned downstream of the inlet. Moreover, increasing the continuous phase flow rate consistently reduced droplet size and increased generation frequency, regardless of the current loop’s position.
{"title":"Droplet generation in a co-flowing microchannel under the non-uniform magnetic fields produced by an electric current loop","authors":"Mehdi Fadaei, Sahand Majidi, Hadi Shoeibi","doi":"10.1016/j.jmmm.2024.172645","DOIUrl":"10.1016/j.jmmm.2024.172645","url":null,"abstract":"<div><div>Micro-magnetofluidics, the study of fluid behavior under magnetic fields in microscale systems, is vital for applications like drug delivery, chemical synthesis, and lab-on-a-chip technologies. Controlling droplet size and formation frequency in these systems is challenging due to the complex interplay of magnetic forces and fluid dynamics. This study introduces a novel approach to control droplet generation in a co-flowing microchannel under a non-uniform magnetic field generated by an electric current loop. Critical parameters such as electric current intensity, continuous phase flow rate, and current loop position are systematically examined for their impact on droplet behavior. The results highlight the unique influence of the magnetic field configuration, specifically the electric current loop, in inducing a transition from dripping to jetting flow patterns with increasing current intensity, leading to larger droplets and reduced generation frequency. Additionally, a distinct behavior of droplet coalescence near the current loop, followed by re-separation, is observed when the loop is positioned downstream of the inlet. Moreover, increasing the continuous phase flow rate consistently reduced droplet size and increased generation frequency, regardless of the current loop’s position.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172645"},"PeriodicalIF":2.5,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660157","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 : 2024-11-04DOI: 10.1016/j.jmmm.2024.172640
Tiancong Li, Jieqiong Gao, Xiaohong Li, Jinyi wang, Li Lou, Yingxin Hua, Yiran Li, Wenyue Qin, Defeng Guo, Wei Li
In the realm of Sm2Co17 nanocomposite magnetic materials, it remains a challenge to fabricate anisotropic magnets by forming nanocrystalline Sm2Co17 phases with strong texture, alongside soft phases of small size and high soft phase content. In this paper, we present a novel approach for fabricating anisotropic Sm2Co17/Fe(Co) nanocomposite bulk magnets with a prominent (00l) texture of the Sm2Co17 phase, the 25 wt% content of the Fe(Co) phase, and a refined grain size of 25 nm. This fabrication is achieved using a two-step high-pressure thermal compression (HPTC) deformation process. The fabricated magnets exhibit a maximum energy product [(BH)max] of 20.0 MGOe with a pronounced magnetic anisotropy (Br///Br⊥ = 1.23). This result is 53 % higher than the previously reported largest value [(BH)max = 13.1 MGOe] for Sm2Co17-based nanocomposites. The magnets also exhibit a low remanence temperature coefficient (α = −0.014 %/°C) and a low coercivity temperature coefficient (β = −0.23 %/°C), demonstrating exceptional thermal stability. Our findings may improve the fabrication of anisotropic bulk Sm2Co17 nanostructure magnets for practical applications.
{"title":"High-performance anisotropic Sm2Co17/Fe(Co) bulk nanocomposite magnets fabricated by two-step high-pressure thermal compression deformation","authors":"Tiancong Li, Jieqiong Gao, Xiaohong Li, Jinyi wang, Li Lou, Yingxin Hua, Yiran Li, Wenyue Qin, Defeng Guo, Wei Li","doi":"10.1016/j.jmmm.2024.172640","DOIUrl":"10.1016/j.jmmm.2024.172640","url":null,"abstract":"<div><div>In the realm of Sm<sub>2</sub>Co<sub>17</sub> nanocomposite magnetic materials, it remains a challenge to fabricate anisotropic magnets by forming nanocrystalline Sm<sub>2</sub>Co<sub>17</sub> phases with strong texture, alongside soft phases of small size and high soft phase content. In this paper, we present a novel approach for fabricating anisotropic Sm<sub>2</sub>Co<sub>17</sub>/Fe(Co) nanocomposite bulk magnets with a prominent (00<em>l</em>) texture of the Sm<sub>2</sub>Co<sub>17</sub> phase, the 25 wt% content of the Fe(Co) phase, and a refined grain size of 25 nm. This fabrication is achieved using a two-step high-pressure thermal compression (HPTC) deformation process. The fabricated magnets exhibit a maximum energy product [(<em>BH</em>)<sub>max</sub>] of 20.0 MGOe with a pronounced magnetic anisotropy (<em>B</em><sub>r</sub><sup>//</sup>/<em>B</em><sub>r</sub><sup>⊥</sup> = 1.23). This result is 53 % higher than the previously reported largest value [(<em>BH</em>)<sub>max</sub> = 13.1 MGOe] for Sm<sub>2</sub>Co<sub>17</sub>-based nanocomposites. The magnets also exhibit a low remanence temperature coefficient (<em>α</em> = −0.014 %/°C) and a low coercivity temperature coefficient (<em>β</em> = −0.23 %/°C), demonstrating exceptional thermal stability. Our findings may improve the fabrication of anisotropic bulk Sm<sub>2</sub>Co<sub>17</sub> nanostructure magnets for practical applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172640"},"PeriodicalIF":2.5,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660158","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 : 2024-11-03DOI: 10.1016/j.jmmm.2024.172641
Qingyang Meng , Wei Sun , Xucai Kan , Xiansong Liu , Sheng Gao , Hongjian Yang , Jian Yang , Zhixiang Wang , Yujie Liu
The present study explores the impact of varying heat treatment temperatures on the magnetic properties, structural configuration and dielectric characteristics of Sr0.67La0.33Fe11.7Zn0.1Co0.2O19 ferrite. M-type ferrite was synthesized using the traditional solid-state method, with thermal treatment temperatures incrementally increasing from 1230 °C to 1310 °C. Pure M-phase strontium ferrite was achieved at temperatures above 1250 °C. The ideal pre-sintering temperature was identified as 1270 °C, where several factors coalesced to enhance the magnetic properties, including the completion of the solid-state reaction and the diminution of the easily magnetized c-axis, which together fostered the intensification of the superexchange interaction. At this temperature, the magnetic properties reached their zenith, with a saturation magnetization (Ms) of 84.81 emu/g, a remanence (Br) of 419 mT, and a coercivity (Hcj) of 3301 Oe. Additionally, the dielectric constant was significantly high at low frequencies but rapidly declined with increasing frequency, achieving its optimal performance at 1270 °C.
本研究探讨了不同热处理温度对 Sr0.67La0.33Fe11.7Zn0.1Co0.2O19 铁氧体的磁性能、结构构型和介电特性的影响。M 型铁氧体是用传统的固态方法合成的，热处理温度从 1230 °C 递增到 1310 °C。纯 M 相锶铁氧体是在 1250 ℃ 以上的温度下合成的。理想的预烧结温度为 1270 ℃，在这一温度下，多个因素共同作用，增强了磁性能，包括固态反应的完成和易磁化 c 轴的减弱，这些因素共同促进了超交换相互作用的增强。在此温度下，磁性能达到顶峰，饱和磁化（Ms）为 84.81 emu/g，剩磁（Br）为 419 mT，矫顽力（Hcj）为 3301 Oe。此外，介电常数在低频时明显较高，但随着频率的增加而迅速下降，在 1270 °C 时达到最佳性能。
{"title":"The influence of pre-sintering temperature on the structural, magnetic, and dielectric properties of Sr0.67La0.33Fe11.7Zn0.1Co0.2O19 ferrite","authors":"Qingyang Meng , Wei Sun , Xucai Kan , Xiansong Liu , Sheng Gao , Hongjian Yang , Jian Yang , Zhixiang Wang , Yujie Liu","doi":"10.1016/j.jmmm.2024.172641","DOIUrl":"10.1016/j.jmmm.2024.172641","url":null,"abstract":"<div><div>The present study explores the impact of varying heat treatment temperatures on the magnetic properties, structural configuration and dielectric characteristics of Sr<sub>0.67</sub>La<sub>0.33</sub>Fe<sub>11.7</sub>Zn<sub>0.1</sub>Co<sub>0.2</sub>O<sub>19</sub> ferrite. M-type ferrite was synthesized using the traditional solid-state method, with thermal treatment temperatures incrementally increasing from 1230 °C to 1310 °C. Pure M-phase strontium ferrite was achieved at temperatures above 1250 °C. The ideal pre-sintering temperature was identified as 1270 °C, where several factors coalesced to enhance the magnetic properties, including the completion of the solid-state reaction and the diminution of the easily magnetized c-axis, which together fostered the intensification of the superexchange interaction. At this temperature, the magnetic properties reached their zenith, with a saturation magnetization (<em>M<sub>s</sub></em>) of 84.81 emu/g, a remanence (<em>B<sub>r</sub></em>) of 419 mT, and a coercivity (<em>H<sub>cj</sub></em>) of 3301 Oe. Additionally, the dielectric constant was significantly high at low frequencies but rapidly declined with increasing frequency, achieving its optimal performance at 1270 °C.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172641"},"PeriodicalIF":2.5,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652559","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 : 2024-11-03DOI: 10.1016/j.jmmm.2024.172639
Luis T. Quispe , Leonardo F. Antunes , A.A. Baldárrago-Alcántara , Wagner C. Macedo , Marcelo A. Rosa , Querem H.F. Rebelo , Leonardo U. Lopes , Sérgio M. Souza , Paulo A.P. Wendhausen
A crucial figure of merit of rare-earth magnets is their magnetic texture, because it is closely related to the maximum remanence a magnet can achieve, hence assessing the magnetic texture is pivotal in terms of magnet’s performance. Fernengel et al. (1996) developed a methodology based on magnetometry, which allows for a quick determination of the texture by calculating the degree of alignment 〈cosθ〉 from the remanent magnetization in directions parallel and perpendicular to the texture axis of the magnet. Although this method provided reliable values, its application was limited to magnets with high degrees of alignment (〈cosθ〉 > 95 %), a restriction that was corrected by Quispe et al. (2020). Nevertheless, recent experiments have indicated that the magnetometry technique can introduce errors in texture assessment when the magnet presents high levels of coercivity. This work presents an approach that incorporates a correction factor into the magnetometry technique, accounting for the effect of the coercivity and circumventing this error source in texture assessment. The proposed methodology has been successfully applied to magnets with varying levels of coercivity.
{"title":"Revisiting the assessment of magnetic texture of Rare-Earth Magnets: The role of coercivity","authors":"Luis T. Quispe , Leonardo F. Antunes , A.A. Baldárrago-Alcántara , Wagner C. Macedo , Marcelo A. Rosa , Querem H.F. Rebelo , Leonardo U. Lopes , Sérgio M. Souza , Paulo A.P. Wendhausen","doi":"10.1016/j.jmmm.2024.172639","DOIUrl":"10.1016/j.jmmm.2024.172639","url":null,"abstract":"<div><div>A crucial figure of merit of rare-earth magnets is their magnetic texture, because it is closely related to the maximum remanence a magnet can achieve, hence assessing the magnetic texture is pivotal in terms of magnet’s performance. Fernengel <em>et al</em>. (1996) developed a methodology based on magnetometry, which allows for a quick determination of the texture by calculating the degree of alignment 〈cosθ〉 from the remanent magnetization in directions parallel and perpendicular to the texture axis of the magnet. Although this method provided reliable values, its application was limited to magnets with high degrees of alignment (〈cosθ〉 > 95 %), a restriction that was corrected by Quispe <em>et al</em>. (2020). Nevertheless, recent experiments have indicated that the magnetometry technique can introduce errors in texture assessment when the magnet presents high levels of coercivity. This work presents an approach that incorporates a correction factor into the magnetometry technique, accounting for the effect of the coercivity and circumventing this error source in texture assessment. The proposed methodology has been successfully applied to magnets with varying levels of coercivity.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"612 ","pages":"Article 172639"},"PeriodicalIF":2.5,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660802","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 : 2024-11-03DOI: 10.1016/j.jmmm.2024.172628
A. Samih , E. Salmani , Hussein. Sabbah , R. El Fdil , Z. Fadil , Fohad Mabood Husain , Seong Cheol Kim , Chaitany Jayprakash Raorane
Half-Heusler CoFeTe alloy is analyzed using Density Functional Theory (DFT) calculations based on the GGA-PBE and GGA + U approximations. The results reveal that CoFeTe was most stable in the β-phase with a ferromagnetic configuration. As determined by the density of states analysis, metallic behavior is observed for the GGA-PBE approximation, whereas a semi metallic nature is observed for the GGA + U approximation. Phonon dispersion, elastic, and mechanical analyses confirm the dynamical and mechanical stability of the alloy. The thermoelectric properties suggest that CoFeTe shows potential for thermoelectric applications, with an increasing Seebeck coefficient and power factor, reaching a ZT value of 0.2 at 800 K. These findings highlight the potential of CoFeTe for applications in thermoelectric devices.
利用基于 GGA-PBE 和 GGA + U 近似的密度泛函理论（DFT）计算分析了半休斯勒 CoFeTe 合金。结果表明，CoFeTe 在具有铁磁性构型的 β 相中最为稳定。根据态密度分析确定，GGA-PBE 近似值观察到金属行为，而 GGA + U 近似值观察到半金属性质。声子色散、弹性和机械分析证实了合金的动力学和机械稳定性。热电性能表明 CoFeTe 具有热电应用潜力，其塞贝克系数和功率因数不断增加，在 800 K 时 ZT 值达到 0.2。
{"title":"First-principles study of structural, elastic, mechanical, electronic, magnetic, optical, and thermoelectric properties of CoFeTe half-heusler alloy","authors":"A. Samih , E. Salmani , Hussein. Sabbah , R. El Fdil , Z. Fadil , Fohad Mabood Husain , Seong Cheol Kim , Chaitany Jayprakash Raorane","doi":"10.1016/j.jmmm.2024.172628","DOIUrl":"10.1016/j.jmmm.2024.172628","url":null,"abstract":"<div><div>Half-Heusler CoFeTe alloy is analyzed using Density Functional Theory (DFT) calculations based on the GGA-PBE and GGA + U approximations. The results reveal that CoFeTe was most stable in the β-phase with a ferromagnetic configuration. As determined by the density of states analysis, metallic behavior is observed for the GGA-PBE approximation, whereas a semi metallic nature is observed for the GGA + U approximation. Phonon dispersion, elastic, and mechanical analyses confirm the dynamical and mechanical stability of the alloy. The thermoelectric properties suggest that CoFeTe shows potential for thermoelectric applications, with an increasing Seebeck coefficient and power factor, reaching a ZT value of 0.2 at 800 K. These findings highlight the potential of CoFeTe for applications in thermoelectric devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172628"},"PeriodicalIF":2.5,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587243","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.2024.172636
Mohammad Reza Karafi, Mina Poursadr
In this paper, a bulk magnetostrictive material is used to measure bending forces. It is made of a cylindrical vanadium permendur alloy. In this sensor, two comb shape magnetic cores and excitation coils are used to create magnetic fields in the material’s surface layer. When bending force is applied to the material, created stresses causes a change in the magnetic flux density on the surface of the material. Induced voltage changes in the pickup coils are used as the output of the sensor. The range of the sensor is up to 280 Newtons. The accuracy of the bending sensor is The bending force measurement sensitivity of the sensor is . By performing combined loading tests, it was found that the sensor is able to detect bending force in both directions. The outputs of the two directions are decoupled and only 4.7 % is affected by each other.
{"title":"A novel bulk magnetostrictive sensor for bending applications","authors":"Mohammad Reza Karafi, Mina Poursadr","doi":"10.1016/j.jmmm.2024.172636","DOIUrl":"10.1016/j.jmmm.2024.172636","url":null,"abstract":"<div><div>In this paper, a bulk magnetostrictive material is used to measure bending forces. It is made of a cylindrical vanadium permendur alloy. In this sensor, two comb shape magnetic cores and excitation coils are used to create magnetic fields in the material’s surface layer. When bending force is applied to the material, created stresses causes a change in the magnetic flux density on the surface of the material. Induced voltage changes in the pickup coils are used as the output of the sensor. The range of the sensor is up to 280 Newtons. The accuracy of the bending sensor is <span><math><mrow><mo>±</mo><mn>5.1</mn><mo>%</mo><mi>F</mi><mi>S</mi><mo>.</mo></mrow></math></span> The bending force measurement sensitivity of the sensor is <span><math><mrow><mn>7.5</mn><mi>m</mi><mi>V</mi><mo>/</mo><mi>N</mi></mrow></math></span>. By performing combined loading tests, it was found that the sensor is able to detect bending force in both directions. The outputs of the two directions are decoupled and only 4.7 % is affected by each other.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172636"},"PeriodicalIF":2.5,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578594","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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