Journal of Magnetism and Magnetic Materials最新文献

{"title":"Predictions of spin-valley properties in ferromagnetic Janus 2H-CeXY (X, Y = Cl, Br, I, X ≠ Y) monolayers: Merger of valleytronics with spintronics","authors":"Huifang Wu ,&nbsp;Ruifeng Yan ,&nbsp;Yankai Chen,&nbsp;Yukai An","doi":"10.1016/j.jmmm.2024.172600","DOIUrl":"10.1016/j.jmmm.2024.172600","url":null,"abstract":"<div><div>In this work, the Janus 2H-CeXY monolayers are predicted as 2D intrinsic ferrovalley materials with bipolar ferromagnetic (FM) semiconductor characters, high T_c of 511–540 K, robust in-plane/perpendicular magnetic anisotropy (IMA/PMA) and spontaneous valley polarization through first-principles calculations. The <em>d</em>-<em>p</em>-<em>d</em> indirect exchange interaction between the Ce atom and X(Y) atoms is responsible for the observed FM ordering. Applying the biaxial strain <em>ε</em> from −6 % to 6 %, the Janus 2H-CeXY monolayers keep energy bandgap and large magnetic anisotropy. While a transition from PMA to IMA character is observed for the 2H-CeBrCl monolayer, which is due to the competition between Ce-<em>p</em>/<em>d</em> and Br/Cl-p orbitals. The intrinsic magnetic interaction and strong SOC effect induce a large spontaneous valley polarization of 29.1–78.7 meV for the Janus 2H-CeXY monolayers, which is also robust under various <em>ε</em>. Besides, the anomalous valley Hall effect (AVHE) can be observed due to the nonzero <em>Ω_z</em>(<em>k</em>) induced by the broken space/time-reversal symmetry. Overall, the Janus 2H-CeXY monolayers provides a new candidate for the spintronic and valleytronic devices.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172600"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535057","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}

{"title":"The detection of magnetic gradient aided by correlated random walk","authors":"Fei Wan ,&nbsp;Li-Hua Lu ,&nbsp;Can Xie ,&nbsp;You-Quan Li","doi":"10.1016/j.jmmm.2024.172586","DOIUrl":"10.1016/j.jmmm.2024.172586","url":null,"abstract":"<div><div>We propose a novel method for sensing the gradient direction of a weak magnetic field overwhelmed by a noisy background through studying the correlated random walk of Brown particles that carry with magnetic moment. Using numerical simulation, we find that the snapshot of the distribution of Brown particles that touched the top surface of a cubic container provides useful information, i.e., the center of the distribution pattern will deflect towards the direction of magnetic gradient. We also find that the impact of magnetic noise can be effectively suppressed by the presence of correlation when the concentration of Brown particles is in the region of <span><math><mrow><mn>0</mn><mo>.</mo><mn>2</mn><msub><mrow><mi>ρ</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>&lt;</mo><mi>ρ</mi><mo>&lt;</mo><mn>0</mn><mo>.</mo><mn>7</mn><msub><mrow><mi>ρ</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span>. Our findings may motivate novel scheme to identify the direction of magnetic gradient in the presence of strong noise, which is undoubtedly important for practical applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172586"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535059","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}

{"title":"Anisotropic model of nonlinear permanent magnets in finite element method software","authors":"Anar Westerberg ,&nbsp;Sai Ram Boggavarapu ,&nbsp;Sandra Eriksson","doi":"10.1016/j.jmmm.2024.172597","DOIUrl":"10.1016/j.jmmm.2024.172597","url":null,"abstract":"<div><div>Rare earth elements are associated with many challenges, and therefore, rare earth free options are being investigated as an alternative. The further improvement of the electrical machines with rare earth free permanent magnets requires an accurate and efficient finite element method (FEM) model to predict and overcome the issues related to a low magnetic flux density or partial demagnetization of permanent magnets. The main challenges of the permanent magnet model development are related to the nonlinearity of the hysteresis loop in the operating region and permanent magnet anisotropy. The model presented in this paper is a dynamic model of anisotropic nonlinear permanent magnet (PM) developed in COMSOL Multiphysics 6.2 software. The model can be used for modelling magnetic materials with a hysteresis loop. Measurement results of Alnico 8 LNGT40 nonlinear permanent magnet were used in this model. The model includes all four quadrants of hysteresis loops, recoil lines, and knee points of preferred or easy (EA) and transverse or hard (HA) magnetization directions. It allows correct modelling of not only generators but also motors and memory machines. The flowcharts of the permanent magnet modelling logic were presented for both directions. Partial demagnetization in the preferred (EA) direction and partial magnetization in the transverse (HA) direction can be observed in the simulation results after the short circuit. Partial remagnetization of the magnet in the preferred (EA) direction and partial demagnetization in the transverse (HA) can be observed after applying a current with the same amplitude but in the opposite direction. The top part of the magnet was mostly affected by the magnetic field of the stator. Simulation results differ from the previous version of the magnet model. The new version of the model has a higher accuracy and shows higher demagnetization in the preferred (EA) direction than the previous version.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172597"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ion-Doped Iron-Based nanoparticles with enhanced magnetic properties: Synthesis and formation mechanism via coprecipitation","authors":"Zhuang Deng ,&nbsp;Yu Wang ,&nbsp;Shuo Zhang ,&nbsp;Jingyi Wu ,&nbsp;Shuning Wei ,&nbsp;Zhen Jiao","doi":"10.1016/j.jmmm.2024.172588","DOIUrl":"10.1016/j.jmmm.2024.172588","url":null,"abstract":"<div><div>Iron-based magnetic nanoparticles have gained significant attention in biomedicine. However, the magnetic properties of iron-based nanoparticles prepared through coprecipitation methods often do not meet application requirements. This study aims to enhance the performance of iron-based magnetic nanoparticles by synthesizing them via the coprecipitation method and doping them with Mn²⁺, Zn²⁺, and Co²⁺ ions in various ratios. Among these, Zn-doped nanoparticles with a 0.6 ratio (ZION-6) exhibits the highest saturation magnetization intensity of 98 emu/g sample and the highest r₂ values of 165.2 mM⁻¹·s⁻¹, making them an effective T₂ MRI contrast agent. Our investigation into the coprecipitation process revealed a formation mechanism for ion-doped magnetic iron-based nanoparticles. This mechanism involves the formation of an intermediate phase, α-FeOOH, followed by phase transformation, ion doping, and the aggregation of small particles to yield the final magnetic nanoparticles. This research could pave the way for developing magnetic nanoparticles with improved properties for biomedical applications.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172588"},"PeriodicalIF":2.5,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535056","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}

{"title":"Strain detection based on magnetic domain wall motion in amorphous FeSiBNb thin film","authors":"Kouya Maeno ,&nbsp;Yuji Fujiwara ,&nbsp;Mutsuko Jimbo ,&nbsp;Daiki Oshima ,&nbsp;Takeshi Kato","doi":"10.1016/j.jmmm.2024.172604","DOIUrl":"10.1016/j.jmmm.2024.172604","url":null,"abstract":"<div><div>The strain dependence of the pulse voltage induced in a pickup coil originating from the domain wall motion in an amorphous FeSiBNb thin film was investigated. No significant change in the peak pulse voltage was observed when tensile strain was applied to the thin film, whereas the peak pulse voltage changed steeply when compressive strain was applied. In addition, strain susceptibility could be controlled via appropriate annealing. Evaluation of the strain gauge comprising the amorphous FeSiBNb thin film, a pickup coil, an electrical circuit (which converts the pulse voltage into direct current voltage), and a Helmholtz coil revealed that strain gauge has a notably high gauge factor of approximately 37,500.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172604"},"PeriodicalIF":2.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535060","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}

{"title":"Fabrication with magnetic-spin coating: Influence of magnetic-inertia energy ratio on gold-pickering ferrofluid droplet assembly morphology","authors":"Paul Okpozo ,&nbsp;James Njuguna ,&nbsp;Sheikh Islam ,&nbsp;Kindness Uyanga ,&nbsp;Ketan Pancholi","doi":"10.1016/j.jmmm.2024.172577","DOIUrl":"10.1016/j.jmmm.2024.172577","url":null,"abstract":"<div><div>Magnetic self-assembly of nanoparticles is a well-known technique for creating thin-film array-patterned functional microstructures. However, an uncontrollable hierarchical assembly formation of magnetically stimulated particles has hindered the desired formation of free-standing two-dimensional (2D) array patterns in thin-film layers. In this study, we proposed a fluidic shearing effect from spin coating to reduce the magnetically stimulated particles’ disarrayed and complex chain formations. This would thus promote linear array formations, even as the film becomes thinner. A series of tests were conducted on a gold-pickering ferrofluid emulsion (GPFE) dispersed in 15.2 mPas aqueous polyvinyl alcohol (PVAh) under varying spin speeds and magnetic setups such as single (SI), compound (CC), and concentric (CR). These setups were chosen to observe the influence of magnetic field strength and distribution on the generated pattern profile from microscopic binary images of the resulting thin films. The aim was to quantify the formed chain thickness (ChT), chain gaps (ChG), and chain lengths (ChL) to capture the morphology and geometrical features of the formed patterns. Our results showed that the quantified values of these profiles and their dimensionless relationships were significantly influenced by the ratio between the applied magnetic packing energy and the centrifugally controlled fluidic energy, Q_PD. This investigation showed that ChT/ChG for a corresponding Q_PD value is 98.6% the same for all configurations, and CR was the best setup going forward, as it yielded the lowest array quality defectivity of 14%. Therefore, we assert that this fabrication method offers flexibility, cost-effectiveness, and expandability in generating linear array patterns that contain graduating variability in grating order dimensions within a single cast that can serve efficiently as a substrate for biomolecules under enhanced Raman and Infrared spectroscopies.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172577"},"PeriodicalIF":2.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tuning the magnetic properties of ultrathin magnetic films with MgO as the buffer layer","authors":"Wang Yao ,&nbsp;Yanru Li ,&nbsp;Meiyin Yang ,&nbsp;Feiyan Hou ,&nbsp;Tao Li ,&nbsp;Tai Min","doi":"10.1016/j.jmmm.2024.172599","DOIUrl":"10.1016/j.jmmm.2024.172599","url":null,"abstract":"<div><div>To minimize the screening effect of a metallic ferromagnetic film and improve the effectiveness of electric field modulation, high-quality ultrathin magnetic film is one of the critical prerequisites. Here ultrathin magnetic films and synthetic antiferromagnetics (SAFs) are deposited on SiO₂ substrates at room temperature using the magnetron sputtering. Atomic force microscopy is used to characterize the roughness of MgO, Nb, Ru, W, and CoFeB films, revealing their atomic-level flatness, with root mean square roughness values below 0.3 nm, which are crucial in the subsequent preparation of ultrathin SAF to achieve high-quality interfaces. The results from the magneto-optical Kerr microscopy suggest that when MgO is 1.48 nm, ultrathin 0.6 nm CoFeB exhibits stable room-temperature perpendicular magnetic anisotropy (PMA) and there is a correlation between room-temperature ferromagnetism and MgO thickness. For SAFs, ultrathin 0.6 nm CoFeB-based SAF exhibits room-temperature antiferromagnetism via the Ruderman-Kittel-Kasuya-Yosida interaction mechanism. The exchange coupling field demonstrates that the transition between ferromagnetic coupling and antiferromagnetic coupling can be regulated by adjusting both the thickness of the non-magnetic spacer layer and the CoFeB layer. This work lays the ground for the potential applications of high-density storage and efficient electric field modulation of ferromagnetic multilayers for improving energy efficiency.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172599"},"PeriodicalIF":2.5,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535054","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}

{"title":"Strategy for co-enhancement of interface adhesion and coercivity of Nd-Fe-B grain boundary diffusion magnet: TbH3 nanopowders used in screen printing","authors":"Haihui Wu ,&nbsp;Zhanjia Wang ,&nbsp;Weiqiang Liu ,&nbsp;Min Fan ,&nbsp;Yuqing Li ,&nbsp;Ming Ji ,&nbsp;Ruihua Du ,&nbsp;Dongtao Zhang ,&nbsp;Guanzhi Xiang ,&nbsp;Ming Yue ,&nbsp;Xiaofei Yi ,&nbsp;Youhao Liu ,&nbsp;Shanshun Zha","doi":"10.1016/j.jmmm.2024.172595","DOIUrl":"10.1016/j.jmmm.2024.172595","url":null,"abstract":"<div><div>Screen printing technology (SPT) was applied to conduct grain boundary diffusion sintered Nd-Fe-B magnets using TbH₃ and TbF₃ nanopowders as diffusion sources. TbH₃ grain boundary diffusion (HGBD) coating had better adhesion to the magnet surface than TbF₃ grain boundary diffusion (FGBD) coating. When the weight gain ratio was 1.0 wt%, the HGBD magnet achieved a coercivity increment of 11.07 kOe under non-pressurized heat treatment, while effectively controlling the magnet’s residual C and O elements. However, pressure heat treatment was necessary for the FGBD magnet to improve the coercivity due to the poor adhesion between the coating and the magnet surface, resulting in more residual C and O elements inside the magnet. Moreover, the coercivity of the FGBD magnet only increased by 7.96 kOe. Compared to the FGBD magnet, Tb diffused deeper into the HGBD magnet and formed more (Nd, Tb)₂Fe₁₄B-Nd₂Fe₁₄B core–shell structures. The formation of core–shell structures greatly enhanced the nucleation field of the reverse domain, thereby increasing the coercivity. Hence, the HGBD magnet had a higher coercivity increment. In addition, the HGBD magnet possessed better coercivity temperature stability than the original and FGBD magnets. Using TbH₃ nanopowders as a diffusion source for SPT can achieve higher magnetic properties and simplified processes without pressure.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"610 ","pages":"Article 172595"},"PeriodicalIF":2.5,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441544","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}

{"title":"Magnetic and mechanical properties of nanotwin SiO2-FeCoNi(AlSi)0.4 high entropy alloy prepared by mechanical alloying and spark plasma sintering","authors":"Rui Wang ,&nbsp;Qiqi Chen ,&nbsp;Xini Xiong ,&nbsp;Mengmeng Meng ,&nbsp;Shaofeng Yang","doi":"10.1016/j.jmmm.2024.172596","DOIUrl":"10.1016/j.jmmm.2024.172596","url":null,"abstract":"<div><div>High-entropy alloys (HEAs), comprised of ferromagnetic metals such as Fe, Co, and Ni, demonstrate remarkable combinations of magnetic and mechanical properties. In this study, we explored the microstructure and magnetic characteristics of SiO₂-FeCoNi(AlSi)_0.4 core–shell HEAs fabricated via mechanical alloying (MA) and spark plasma sintering (SPS). Thermodynamic analysis revealed that the FeCoNi(AlSi)_0.4 core–shell alloy system exhibits a higher ΔS (11.75 kJ/mol), indicating that forming a solid solution structure is easy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the development of a face-centered cubic (FCC) solid solution with a highly deformed nanotwin structure after SPS as-sintered. The vibrating sample magnetometer (VSM) test indicated an elevated soft magnetic behavior for FeCoNi(AlSi)_0.4 core–shell HEAs as-sintered, with a magnetic saturation (MS) of 140.2 emu/g and a coercivity field (HC) of 1.35 Oe in an applied magnetic field of 2 T. The ultimate shear strength and tensile strengths were found to be 1552.4 MPa and 1278.9 MPa, respectively. This investigation conclusively highlights that the lower fault energy of the FeCoNi(AlSi)_0.4 alloy system significantly influences the mechanical and magnetic properties of HEAs.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"611 ","pages":"Article 172596"},"PeriodicalIF":2.5,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535055","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}

{"title":"Half-metallic behavior and anisotropy of two-dimensional MoSi2N4/ScSi2N4 heterojunction","authors":"Haiming Huang ,&nbsp;Wenyu Zhao ,&nbsp;Mingyang Yang ,&nbsp;Songtao Xue ,&nbsp;Zedong He ,&nbsp;Amel Laref","doi":"10.1016/j.jmmm.2024.172592","DOIUrl":"10.1016/j.jmmm.2024.172592","url":null,"abstract":"<div><div>Heterojunctions formed by stacking different two-dimensional monolayer materials typically have tunable electronic properties, which will greatly broaden the application prospects of 2D materials in electron devices. In this paper, the structures, electron properties, and anisotropy of MoSi₂N₄/ScSi₂N₄ heterojunctions formed by stacking MoSi₂N₄ monolayer with semiconductor properties and ScSi₂N₄ monolayer with half-metallic properties have been systematically studied. The results show that Type-Ⅰ configuration has the most stable structure in terms of total energy, binding energy, phonon spectrum and molecular dynamics among the three configurations formed by MoSi₂N₄/ScSi₂N₄ heterojunctions. The MoSi₂N₄/ScSi₂N₄ heterojunction has robust half-metallic behavior and tensile anisotropy at equilibrium. At the same time, MoSi₂N₄/ScSi₂N₄ heterojunction can still maintain stable ferromagnetic and half-metallic properties under large interlayer distance changes. Studies of magnetic anisotropy show that the direction of hard axis for MoSi₂N₄/ScSi₂N₄ heterojunction is perpendicular to the 2D layer plane. The tunable properties of MoSi₂N₄/ScSi₂N₄ heterojunction provides promising exploration for novel 2D materials.</div></div>","PeriodicalId":366,"journal":{"name":"Journal of Magnetism and Magnetic Materials","volume":"610 ","pages":"Article 172592"},"PeriodicalIF":2.5,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445570","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}