Pub Date : 2024-10-31DOI: 10.1109/LMAG.2024.3490380
J. Schmidtpeter;Proloy T. Das;Y. Zabila;C. Schubert;T. Gundrum;T. Wondrak;D. Makarov
Planar Hall magnetoresistive sensors (PHMRs) are promising candidates for various magnetic sensing applications due to their high sensitivity, low power consumption, and compatibility with integrated circuit technology. However, their performance is often limited by inherent noise sources, impacting their resolution and overall sensitivity. Here the effect of three bilayer structures NiFe(10 nm)/IrMn(10 nm), NiFe(30 nm)/IrMn(10 nm), and NiFe(30 nm)/IrMn(20 nm) on noise levels is investigated at low frequency (DC-25 Hz). This study includes a detailed investigation on the optimization process and noise characteristics of multiring PHMR sensors, focusing on identifying and quantifying the dominant noise sources. The experimental measurements are complemented by a theoretical analysis of noise sources including thermal noise, 1/ f noise, intermixing, and environmental noise. The best magnetic resolution is observed for the NiFe(30 nm)/IrMn(10 nm) structure, which achieves a detectivity below 1.5 nT/√Hz at 10 Hz in a nonshielded environment at room temperature. In addition, a substantial improvement in sensitivity is observed by annealing the sensors at 250 °C for 1 h. The findings of this study contribute to a deeper understanding of noise behavior in PHMR sensors, paving the way for developing strategies to improve their performance for demanding sensing applications at low frequencies.
{"title":"Exchange-Biased Multiring Planar Hall Magnetoresistive Sensors With Nanotesla Resolution in Nonshielded Environments","authors":"J. Schmidtpeter;Proloy T. Das;Y. Zabila;C. Schubert;T. Gundrum;T. Wondrak;D. Makarov","doi":"10.1109/LMAG.2024.3490380","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3490380","url":null,"abstract":"Planar Hall magnetoresistive sensors (PHMRs) are promising candidates for various magnetic sensing applications due to their high sensitivity, low power consumption, and compatibility with integrated circuit technology. However, their performance is often limited by inherent noise sources, impacting their resolution and overall sensitivity. Here the effect of three bilayer structures NiFe(10 nm)/IrMn(10 nm), NiFe(30 nm)/IrMn(10 nm), and NiFe(30 nm)/IrMn(20 nm) on noise levels is investigated at low frequency (DC-25 Hz). This study includes a detailed investigation on the optimization process and noise characteristics of multiring PHMR sensors, focusing on identifying and quantifying the dominant noise sources. The experimental measurements are complemented by a theoretical analysis of noise sources including thermal noise, 1/\u0000<italic>f</i>\u0000 noise, intermixing, and environmental noise. The best magnetic resolution is observed for the NiFe(30 nm)/IrMn(10 nm) structure, which achieves a detectivity below 1.5 nT/√Hz at 10 Hz in a nonshielded environment at room temperature. In addition, a substantial improvement in sensitivity is observed by annealing the sensors at 250 °C for 1 h. The findings of this study contribute to a deeper understanding of noise behavior in PHMR sensors, paving the way for developing strategies to improve their performance for demanding sensing applications at low frequencies.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142798050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-24DOI: 10.1109/LMAG.2024.3484957
Steven Louis;Hannah Bradley;Cody Trevillian;Andrei Slavin;Vasyl Tyberkevych
This letter presents a novel spiking artificial neuron design based on a combined spin valve/magnetic tunnel junction (SV/MTJ). Traditional hardware used in artificial intelligence and machine learning faces significant challenges related to high power consumption and scalability. To address these challenges, spintronic neurons, which can mimic biologically inspired neural behaviors, offer a promising solution. We present a model of an SV/MTJ-based neuron that uses technologies that have been successfully integrated with CMOS in commercially available applications. The operational dynamics of the neuron are derived analytically through the Landau–Lifshitz-Gilbert–Slonczewski equation, demonstrating its ability to replicate key spiking characteristics of biological neurons such as response latency and refractive behavior. Simulation results indicate that the proposed neuron design can operate on a timescale of about 1 ns, without any bias current and with power consumption as low as 50 ${mu }$ W.
{"title":"Spintronic Neuron Using a Magnetic Tunnel Junction for Low-Power Neuromorphic Computing","authors":"Steven Louis;Hannah Bradley;Cody Trevillian;Andrei Slavin;Vasyl Tyberkevych","doi":"10.1109/LMAG.2024.3484957","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3484957","url":null,"abstract":"This letter presents a novel spiking artificial neuron design based on a combined spin valve/magnetic tunnel junction (SV/MTJ). Traditional hardware used in artificial intelligence and machine learning faces significant challenges related to high power consumption and scalability. To address these challenges, spintronic neurons, which can mimic biologically inspired neural behaviors, offer a promising solution. We present a model of an SV/MTJ-based neuron that uses technologies that have been successfully integrated with CMOS in commercially available applications. The operational dynamics of the neuron are derived analytically through the Landau–Lifshitz-Gilbert–Slonczewski equation, demonstrating its ability to replicate key spiking characteristics of biological neurons such as response latency and refractive behavior. Simulation results indicate that the proposed neuron design can operate on a timescale of about 1 ns, without any bias current and with power consumption as low as 50 \u0000<inline-formula><tex-math>${mu }$</tex-math></inline-formula>\u0000W.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142672079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-21DOI: 10.1109/LMAG.2024.3484271
Mohammad Asif;Prashant Kumar;Mirza Tariq Beg;M. Nizamuddin;Bijoy Kumar Kuanr
In the present investigation, we have demonstrated the effect of different substrates (Si, SiO 2${rm{, }};text{and};text {{A}}{{{text {l}}}_{2}}{{{text {O}}}_{3}}$ ) and deposition temperatures ( TD = 27 °C to 450 °C) of sputtered Fe 80 Co 20 ferromagnetic thin films of 30 nm thickness on their microstructural, static, and dynamic properties. The lowest value of Gilbert damping (α eff ) of 5.1 $ times, 10$−3 with a high saturation magnetization ( MS ) is the outcome of the improved atomic ordering and overall film crystallinity with ultralow interfacial roughness (0.23 ± 0.03 nm) of 400 °C grown films. The structural analysis from atomic force microscopy depicts temperature-dependent improvement in films grown at 400 °C. From ferromagnetic resonance and vibrating sample magnetometry experiments, magnetization was determined to be the highest MS$ approx text {1628.8} {rm{emu/cc}}$ for the films grown at 400 °C. We have validated the above-mentioned experimental data through micromagnetic simulation using ubermag and an object-oriented micromagnetic framework that is used in backend for computation.
{"title":"Relaxation Dynamics of Sputtered Fe80Co20 Thin Films on Different Substrates: Micromagnetic Validation","authors":"Mohammad Asif;Prashant Kumar;Mirza Tariq Beg;M. Nizamuddin;Bijoy Kumar Kuanr","doi":"10.1109/LMAG.2024.3484271","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3484271","url":null,"abstract":"In the present investigation, we have demonstrated the effect of different substrates (Si, SiO\u0000<sub>2</sub>\u0000<inline-formula><tex-math>${rm{, }};text{and};text {{A}}{{{text {l}}}_{2}}{{{text {O}}}_{3}}$</tex-math></inline-formula>\u0000) and deposition temperatures (\u0000<italic>T<sub>D</sub></i>\u0000 = 27 °C to 450 °C) of sputtered Fe\u0000<sub>80</sub>\u0000Co\u0000<sub>20</sub>\u0000 ferromagnetic thin films of 30 nm thickness on their microstructural, static, and dynamic properties. The lowest value of Gilbert damping (α\u0000<sub>eff</sub>\u0000) of 5.1 \u0000<inline-formula><tex-math>$ times, 10$</tex-math></inline-formula>\u0000<sup>−3</sup>\u0000 with a high saturation magnetization (\u0000<italic>M<sub>S</sub></i>\u0000) is the outcome of the improved atomic ordering and overall film crystallinity with ultralow interfacial roughness (0.23 ± 0.03 nm) of 400 °C grown films. The structural analysis from atomic force microscopy depicts temperature-dependent improvement in films grown at 400 °C. From ferromagnetic resonance and vibrating sample magnetometry experiments, magnetization was determined to be the highest \u0000<italic>M<sub>S</sub></i>\u0000 \u0000<inline-formula><tex-math>$ approx text {1628.8} {rm{emu/cc}}$</tex-math></inline-formula>\u0000 for the films grown at 400 °C. We have validated the above-mentioned experimental data through micromagnetic simulation using ubermag and an object-oriented micromagnetic framework that is used in backend for computation.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142777579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-17DOI: 10.1109/LMAG.2024.3483069
Mengting Zou;Xilai Bao;Xinze Li;Yali Xie;Huali Yang;Lili Pan;Xiaojian Zhu;Run-Wei Li
Spin valves have received significant attention in the realm of flexible magnetic materials and devices due to their advantages of rapid response and high integration. Despite these benefits, the practical application of spin valves in wearable devices is constrained by their low stretchability and strain stability under tensile strain. Here, by designing spin valves with zigzag-wrinkled structure, we demonstrated that the magnetotransport properties of our spin valves remained unaffected under 25% biaxial tensile strain, revealing stretchability and strain stability. These outstanding performances are related to the zigzag-wrinkled structure generated after releasing the biaxial prestrain in polymer polydimethylsiloxane substrates. The flattening of the zigzag wrinkles under the biaxial tensile strain releases the direct effect of strain on the metal multilayers, thereby maintaining sensing performances upon stretching. This innovative design paves the way for the development of robust, flexible magnetic devices suitable for wearable technology.
{"title":"Biaxially Stretchable Spin Valves With Stable Magnetic Sensing Performance","authors":"Mengting Zou;Xilai Bao;Xinze Li;Yali Xie;Huali Yang;Lili Pan;Xiaojian Zhu;Run-Wei Li","doi":"10.1109/LMAG.2024.3483069","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3483069","url":null,"abstract":"Spin valves have received significant attention in the realm of flexible magnetic materials and devices due to their advantages of rapid response and high integration. Despite these benefits, the practical application of spin valves in wearable devices is constrained by their low stretchability and strain stability under tensile strain. Here, by designing spin valves with zigzag-wrinkled structure, we demonstrated that the magnetotransport properties of our spin valves remained unaffected under 25% biaxial tensile strain, revealing stretchability and strain stability. These outstanding performances are related to the zigzag-wrinkled structure generated after releasing the biaxial prestrain in polymer polydimethylsiloxane substrates. The flattening of the zigzag wrinkles under the biaxial tensile strain releases the direct effect of strain on the metal multilayers, thereby maintaining sensing performances upon stretching. This innovative design paves the way for the development of robust, flexible magnetic devices suitable for wearable technology.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1109/LMAG.2024.3479924
Yang-Ki Hong;Jihoon Park;Hang Nam Ok;Minyeong Choi;Md Abdul Wahed;Myung-Hwa Jung;Chang-Dong Yeo
Monoclinic Fe 3 Se 4 was synthesized using a ceramic method. Mössbauer spectroscopy and density functional theory were used to investigate the physical origins of its ferrimagnetism and high coercivity. At 78 K, 12 Mössbauer absorption lines were observed. These lines are composed of two subspectra, A and B, corresponding to Fe atoms at the 2 a and 4 i sites, respectively. At 320 K, the Mössbauer spectrum collapsed, indicating a transition from a ferrimagnetic to a paramagnetic state. This temperature is close to the Curie temperature ( T C ) of 331 or 315 K reported in the literature. The analysis of local structural symmetry confirmed that the Fe atoms in the 2 a sites are more symmetrically coordinated with neighboring Se atoms than those in the 4 i sites. Therefore, the Fe atoms in the 2 a sites exhibit a higher hyperfine magnetic field (HMF) of 225 kOe and a weaker quadrupole splitting (QS) of 0.17 mm/s than the Fe atoms in the 4 i sites, which exhibit an HMF of 105 kOe and a QS of 0.55 mm/s. Our density functional study confirmed that Fe 3 Se 4 exhibits ferrimagnetic behavior, with a magnetic moment of 4.48 µ B /u.c. and a T C of 354 K. Fe 3 Se 4 shows a high magnetocrystalline anisotropy constant ( K u ) of 0.9 × 10 6 erg/cm 3 . This high K u value is attributed to the Fe atoms at the 4 i sites. It is suggested that the high coercivity of Fe 3 Se 4 , as reported in the literature, is due to the distorted 4 i site, which experiences the Jahn–Teller effect.
采用陶瓷法合成了单斜Fe3Se4。研究人员利用莫斯鲍尔光谱学和密度泛函理论研究了其铁磁性和高矫顽力的物理根源。在 78 K 时，观察到 12 条莫斯鲍尔吸收线。这些线由两个子谱 A 和 B 组成，分别对应于 2a 和 4i 位点上的铁原子。在 320 K 时，莫斯鲍尔光谱坍缩，表明铁磁态向顺磁态过渡。这一温度接近文献报道的居里温度（TC）331 或 315 K。对局部结构对称性的分析证实，与 4i 位点的铁原子相比，2a 位点的铁原子与相邻 Se 原子的配位更对称。因此，2a 位点的铁原子比 4i 位点的铁原子表现出更高的超频磁场（HMF）（225 kOe）和更弱的四极分裂（QS）（0.17 mm/s），后者表现出 105 kOe 的 HMF 和 0.55 mm/s 的 QS。我们的密度泛函研究证实，Fe3Se4 具有铁磁性，磁矩为 4.48 µB/u.c.，TC 为 354 K。这一高 Ku 值归因于 4i 位点上的铁原子。根据文献报道，Fe3Se4 的高矫顽力是由于 4i 位点发生了扭曲，从而产生了贾恩-泰勒效应。
{"title":"Mössbauer and Density Functional Studies of Ferrimagnetic Fe3Se4","authors":"Yang-Ki Hong;Jihoon Park;Hang Nam Ok;Minyeong Choi;Md Abdul Wahed;Myung-Hwa Jung;Chang-Dong Yeo","doi":"10.1109/LMAG.2024.3479924","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3479924","url":null,"abstract":"Monoclinic Fe\u0000<sub>3</sub>\u0000Se\u0000<sub>4</sub>\u0000 was synthesized using a ceramic method. Mössbauer spectroscopy and density functional theory were used to investigate the physical origins of its ferrimagnetism and high coercivity. At 78 K, 12 Mössbauer absorption lines were observed. These lines are composed of two subspectra, A and B, corresponding to Fe atoms at the 2\u0000<italic>a</i>\u0000 and 4\u0000<italic>i</i>\u0000 sites, respectively. At 320 K, the Mössbauer spectrum collapsed, indicating a transition from a ferrimagnetic to a paramagnetic state. This temperature is close to the Curie temperature (\u0000<italic>T</i>\u0000<sub>C</sub>\u0000) of 331 or 315 K reported in the literature. The analysis of local structural symmetry confirmed that the Fe atoms in the 2\u0000<italic>a</i>\u0000 sites are more symmetrically coordinated with neighboring Se atoms than those in the 4\u0000<italic>i</i>\u0000 sites. Therefore, the Fe atoms in the 2\u0000<italic>a</i>\u0000 sites exhibit a higher hyperfine magnetic field (HMF) of 225 kOe and a weaker quadrupole splitting (QS) of 0.17 mm/s than the Fe atoms in the 4\u0000<italic>i</i>\u0000 sites, which exhibit an HMF of 105 kOe and a QS of 0.55 mm/s. Our density functional study confirmed that Fe\u0000<sub>3</sub>\u0000Se\u0000<sub>4</sub>\u0000 exhibits ferrimagnetic behavior, with a magnetic moment of 4.48 µ\u0000<sub>B</sub>\u0000/u.c. and a \u0000<italic>T</i>\u0000<sub>C</sub>\u0000 of 354 K. Fe\u0000<sub>3</sub>\u0000Se\u0000<sub>4</sub>\u0000 shows a high magnetocrystalline anisotropy constant (\u0000<italic>K</i>\u0000<sub>u</sub>\u0000) of 0.9 × 10\u0000<sup>6</sup>\u0000 erg/cm\u0000<sup>3</sup>\u0000. This high \u0000<italic>K</i>\u0000<sub>u</sub>\u0000 value is attributed to the Fe atoms at the 4\u0000<italic>i</i>\u0000 sites. It is suggested that the high coercivity of Fe\u0000<sub>3</sub>\u0000Se\u0000<sub>4</sub>\u0000, as reported in the literature, is due to the distorted 4\u0000<italic>i</i>\u0000 site, which experiences the Jahn–Teller effect.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1109/LMAG.2024.3479932
Kuntal Roy
Topological insulators and giant spin-orbit torque switching of nanomagnets are among the frontier topics for the development of energy-efficient spintronic devices. Spin-circuit representations involving different materials and phenomena are quite well established now for their prowess of interpreting experimental results and then designing complex and efficient functional devices. Here, we construct the spin-circuit representation of spin pumping into topological insulators, considering both the bulk and surface states with parallel channels, which allows for the interpretation of practical experimental results. We show that the high increase in effective spin mixing conductance and inverse spin Hall voltages cannot be explained by the low-conductive bulk states of topological insulators. We determine a high spin Hall angle close to the maximum magnitude of one from experimental results and address the controversy in the literature by correctly estimating the parameters involved in the system. With an eye to designing energy-efficient spin devices, we further employ a spin-sink layer in the spin-circuit formalism to increase the effective spin mixing conductance at low thicknesses and double the inverse spin Hall voltage.
{"title":"Spin-Circuit Representation of Spin Pumping Into Topological Insulators and Determination of Giant Spin Hall Angle and Inverse Spin Hall Voltages","authors":"Kuntal Roy","doi":"10.1109/LMAG.2024.3479932","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3479932","url":null,"abstract":"Topological insulators and giant spin-orbit torque switching of nanomagnets are among the frontier topics for the development of energy-efficient spintronic devices. Spin-circuit representations involving different materials and phenomena are quite well established now for their prowess of interpreting experimental results and then designing complex and efficient functional devices. Here, we construct the spin-circuit representation of spin pumping into topological insulators, considering both the bulk and surface states with parallel channels, which allows for the interpretation of practical experimental results. We show that the high increase in effective spin mixing conductance and inverse spin Hall voltages cannot be explained by the low-conductive bulk states of topological insulators. We determine a high spin Hall angle close to the maximum magnitude of one from experimental results and address the controversy in the literature by correctly estimating the parameters involved in the system. With an eye to designing energy-efficient spin devices, we further employ a spin-sink layer in the spin-circuit formalism to increase the effective spin mixing conductance at low thicknesses and double the inverse spin Hall voltage.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142810338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1109/LMAG.2024.3479922
Carson Rivard;Albrecht Jander;Pallavi Dhagat
Micromagnetic modeling is used to simulate the parametric amplification of forward volume spin waves by a surface acoustic wave (SAW) traveling noncollinearly in a yttrium–iron–garnet thin film. The angle of incidence between the signal spin wave and the SAW pump determines the strength of parametric coupling as well as the propagation direction of the resulting idler spin wave. In a collinear arrangement, where the spin wave and SAW travel together, the acoustic pump amplitude needed to achieve amplification is greater than the threshold for the parametric generation of spin waves from the thermal background. However, in a noncollinear arrangement with >35° angle of incidence between the signal spin wave and SAW pump, the coupling is enhanced and allows for continuous amplification of spin waves by more than 10× without simultaneously resulting in unconstrained growth of thermal spin waves. The angular dependence of the parametric coupling strength, as determined from the simulations, agrees qualitatively with theoretical predictions.
{"title":"Micromagnetic Modeling of Parametric Amplification of Forward Volume Spin Waves by Noncollinear Surface Acoustic Waves","authors":"Carson Rivard;Albrecht Jander;Pallavi Dhagat","doi":"10.1109/LMAG.2024.3479922","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3479922","url":null,"abstract":"Micromagnetic modeling is used to simulate the parametric amplification of forward volume spin waves by a surface acoustic wave (SAW) traveling noncollinearly in a yttrium–iron–garnet thin film. The angle of incidence between the signal spin wave and the SAW pump determines the strength of parametric coupling as well as the propagation direction of the resulting idler spin wave. In a collinear arrangement, where the spin wave and SAW travel together, the acoustic pump amplitude needed to achieve amplification is greater than the threshold for the parametric generation of spin waves from the thermal background. However, in a noncollinear arrangement with >35° angle of incidence between the signal spin wave and SAW pump, the coupling is enhanced and allows for continuous amplification of spin waves by more than 10× without simultaneously resulting in unconstrained growth of thermal spin waves. The angular dependence of the parametric coupling strength, as determined from the simulations, agrees qualitatively with theoretical predictions.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1109/LMAG.2024.3479936
M. J. Vazquez Bernardez;J. Solano;M. Bailleul;N. Vukadinovic;D. Stoeffler;C. Lefevre
Ti–Mn substituted Ba(TiMn) x Fe 12-2x O 19 hexaferrite randomly oriented composites were obtained by conventional ceramic synthesis. At zero applied magnetic field, in its polycrystalline powder form, this ferrimagnetic compound exhibits a multipeak permeability spectrum with two high-frequency resonances that converge under the action of an external magnetic field. We conduct a broad-band ferromagnetic resonances characterization of this system under an applied magnetic field between 0 and 2 T and integrate the results with micromagnetic simulations to investigate the presence of high-frequency resonating magnetic domains contingent upon the sample's microstructure. Simulations show that magnetic domains separated by domain walls upon each magnetic particle are responsible for the multipeak resonance in the Ka-band. By combining the simulated spectra with an effective medium theory accounting for the dilution effect of the dielectric matrix, we reproduce the zero-field permeability spectra.
通过传统陶瓷合成法获得了钛锰取代的 Ba(TiMn)xFe12-2xO19 六价铁氧体无规取向复合材料。在零外加磁场条件下，这种多晶粉末状的铁磁化合物表现出多峰值磁导率谱，其中有两个高频共振，在外加磁场的作用下，这两个共振趋于一致。我们在 0 到 2 T 的外加磁场下对该系统进行了宽带铁磁共振表征，并将结果与微磁模拟相结合，以研究样品的微观结构是否存在高频共振磁畴。模拟结果表明，每个磁性粒子上被磁畴壁隔开的磁畴是产生 Ka 波段多峰共振的原因。通过将模拟光谱与有效介质理论（考虑到介质基体的稀释效应）相结合，我们再现了零场磁导率光谱。
{"title":"Multiresonance Microwave Absorption in Ti–Mn Substituted Barium Hexaferrite Composites","authors":"M. J. Vazquez Bernardez;J. Solano;M. Bailleul;N. Vukadinovic;D. Stoeffler;C. Lefevre","doi":"10.1109/LMAG.2024.3479936","DOIUrl":"https://doi.org/10.1109/LMAG.2024.3479936","url":null,"abstract":"Ti–Mn substituted Ba(TiMn)\u0000<sub><i>x</i></sub>\u0000Fe\u0000<sub>12-2<i>x</i></sub>\u0000O\u0000<sub>19</sub>\u0000 hexaferrite randomly oriented composites were obtained by conventional ceramic synthesis. At zero applied magnetic field, in its polycrystalline powder form, this ferrimagnetic compound exhibits a multipeak permeability spectrum with two high-frequency resonances that converge under the action of an external magnetic field. We conduct a broad-band ferromagnetic resonances characterization of this system under an applied magnetic field between 0 and 2 T and integrate the results with micromagnetic simulations to investigate the presence of high-frequency resonating magnetic domains contingent upon the sample's microstructure. Simulations show that magnetic domains separated by domain walls upon each magnetic particle are responsible for the multipeak resonance in the Ka-band. By combining the simulated spectra with an effective medium theory accounting for the dilution effect of the dielectric matrix, we reproduce the zero-field permeability spectra.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142679319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-13DOI: 10.1109/LMAG.2024.3461575
Yassin Elmeligi;Bushra Hussain;Michael G. Cottam
The properties of the quantized spin-wave frequencies and the transition field between the two stable magnetization states (the low-field vortex state and the higher-field onion state) are studied for elliptical nanorings. The dependences of these quantities on the nanoring sizes and the degree of ellipticity are examined over a wide range of values for the applied magnetic field and its orientation. The novel effects introduced when the symmetry axes of the inner elliptical edges of the rings are rotated relative to those of the outer elliptical edge are also studied. To characterize these effects, our theory makes use of a Hamiltonian-based dipole-exchange methodology, adapted from that used to elucidate the spin-wave modes in circular nanorings. It is found that spin-wave frequencies and the behavior of the transition field(s) depend sensitively on the degree of ellipticity, the rotation angle of the inner elliptical edge with respect to the outer elliptical edge, and the direction of the applied field relative to the nanoring axes.
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Ferromagnetic multilayer thin films with oxide capping layer have potential applications in voltage-controlled magnetic devices. Here, we present the optimization of the magnetic and dielectric properties of CoFeB/MgO thin films with different capping layers (Ta, Al 2 O 3 , and HfO 2 ). We find that the samples with oxide capping layers show a higher perpendicular magnetic anisotropy (PMA) than those with a Ta capping layer. Meanwhile, a high dielectric constant of 58 is obtained in samples capped with 30 nm of HfO 2 . This high dielectric constant is attributed to the formation of an oxygen vacancy-related capacitive double layer in the HfO 2 film according to X-ray diffraction analyses and current–voltage measurements. Finally, we find that the optimal annealing temperature, which allows for both high PMA and dielectric constant, is between 250 °C and 290 °C. Our results could contribute to designing high-performance materials for controlling interfacial magnetic properties in novel spintronic devices.
带有氧化物覆盖层的铁磁多层薄膜在电压控制磁性器件中具有潜在的应用价值。在此，我们介绍了对具有不同覆盖层（Ta、Al2O3 和 HfO2）的 CoFeB/MgO 薄膜的磁性和介电性质的优化。我们发现，具有氧化物封盖层的样品比具有钽封盖层的样品显示出更高的垂直磁各向异性（PMA）。同时，用 30 nm 的 HfO2 覆层的样品获得了 58 的高介电常数。根据 X 射线衍射分析和电流电压测量，这一高介电常数归因于 HfO2 薄膜中形成了与氧空位相关的电容双层。最后，我们发现实现高 PMA 和介电常数的最佳退火温度介于 250 °C 和 290 °C 之间。我们的研究结果有助于设计高性能材料，以控制新型自旋电子器件的界面磁性能。
{"title":"Magnetic and Dielectric Properties of CoFeB Multilayer Thin Films With Oxide Capping Layer","authors":"Yuting Liu;Sylvain Eimer;Jianyuan Zhao;Yiming Chen","doi":"10.1109/LMAG.2024.3459813","DOIUrl":"10.1109/LMAG.2024.3459813","url":null,"abstract":"Ferromagnetic multilayer thin films with oxide capping layer have potential applications in voltage-controlled magnetic devices. Here, we present the optimization of the magnetic and dielectric properties of CoFeB/MgO thin films with different capping layers (Ta, Al\u0000<sub>2</sub>\u0000O\u0000<sub>3</sub>\u0000, and HfO\u0000<sub>2</sub>\u0000). We find that the samples with oxide capping layers show a higher perpendicular magnetic anisotropy (PMA) than those with a Ta capping layer. Meanwhile, a high dielectric constant of 58 is obtained in samples capped with 30 nm of HfO\u0000<sub>2</sub>\u0000. This high dielectric constant is attributed to the formation of an oxygen vacancy-related capacitive double layer in the HfO\u0000<sub>2</sub>\u0000 film according to X-ray diffraction analyses and current–voltage measurements. Finally, we find that the optimal annealing temperature, which allows for both high PMA and dielectric constant, is between 250 °C and 290 °C. Our results could contribute to designing high-performance materials for controlling interfacial magnetic properties in novel spintronic devices.","PeriodicalId":13040,"journal":{"name":"IEEE Magnetics Letters","volume":"15 ","pages":"1-5"},"PeriodicalIF":1.1,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142193671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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