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Improvement of high-frequency properties of Co2FeSi heusler films by ultrathin Ru underlayer

Chinese Physics B 2020年第4期29卷 379-384页

作者： Cuiling Wang Shouheng Zhang Shandong Li Honglei Du Guoxia Zhao Derang Cao College of Physics Center for Marine Observation and CommunicationQingdao UniversityQingdao 266071China College of Electronic and Information Engineering Shandong University of Science and TechnologyQingdao 266510China School of Physics Shandong UniversityJinan 250100China

heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 *** is revealed that the Ru underlayers reduce the grain size of Co2FeSi,dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe(1 Oe=79.5775 A·m^-1)to 582 Oe with an increment ratio of 2.4,while a low damping coefficient *** result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external *** a result,excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved.

关键词： oblique sputtering ferromagnetic resonance Ru underlayer heusler thin film

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A Critical Study of the Elastic Properties and Stability of heusler Compounds: Phase Change and Tetragonal <i>X<sub>2</sub>YZ</i>Compounds

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Journal of Modern Physics 2018年第4期9卷 775-805页

作者： Shuchun Wu S. Shahab Naghavi Gerhard H. Fecher Claudia Felser Max Planck Institute for Chemical Physics of Solids Dresden Germany Department of Materials Science and Engineering Northwestern University Evanston IL USA

In the present work, the elastic constants and derived properties of tetragonal heusler compounds were calculated using the high accuracy of the full-potential linearized augmented plane wave (FPLAPW) method. To find the criteria required for an accurate calculation, the consequences of increasing the numbers of k-points and plane waves on the convergence of the calculated elastic constants were explored. Once accurate elastic constants were calculated, elastic anisotropies, sound velocities, Debye temperatures, malleability, and other measurable physical properties were determined for the studied systems. The elastic properties suggested metallic bonding with intermediate malleability, between brittle and ductile, for the studied heusler compounds. To address the effect of off-stoichiometry on the mechanical properties, the virtual crystal approximation (VCA) was used to calculate the elastic constants. The results indicated that an extreme correlation exists between the anisotropy ratio and the stoichiometry of the heusler compounds, especially in the case of Ni2MnGa. Metastable cubic Ni2MnGa exhibits a very high anisotropy (≈28) and hypothetical cubic Rh2FeSn violates the Born-Huang stability criteria in the L21 structure. The bulk moduli of the investigated tetragonal compounds do not vary much (≈130 ...190 GPa). The averaged values of the other elastic moduli are also rather similar, however, rather large differences are found for the elastic anisotropies of the compounds. These are reflected in very different spatial distributions of Young’s moduli when comparing the different compounds. The slowness surfaces of the compounds also differ considerably even though the average sound velocities are in the same order of magnitude (3.2 ... 3.6 km/s). The results demonstrate the importance of the elastic properties not only for purely tetragonal heusler compounds but also for phase change materials that exhibit magnetic shape memory or magnetocaloric effects.

关键词： Elastic Constants Elastic Stability Tetragonal heusler Compounds Cubic Instability Phase Transition

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合金元素与NiAl-Cr合金中heusler相关系的研究

合金元素与NiAl-Cr合金中Heusler相关系的研究

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作者：谢龙飞辽宁工业大学

学位级别：硕士

本文研究了合金元素Ti、Zr、Mo、Co及其含量对三种不同制备态NiAl-Cr合金中heusler相的稳定性及转变规律的影响。铸态NiAl-Cr-5Ti合金由灰色NiAl基体、灰白色层片状Cr相组成共晶胞组织，没有heusler（Ni2AlTi）相。含10Ti或12Ti的NiAl-C... 详细信息

本文研究了合金元素Ti、Zr、Mo、Co及其含量对三种不同制备态NiAl-Cr合金中heusler相的稳定性及转变规律的影响。铸态NiAl-Cr-5Ti合金由灰色NiAl基体、灰白色层片状Cr相组成共晶胞组织，没有heusler（Ni2AlTi）相。含10Ti或12Ti的NiAl-Cr合金，共晶胞界处有不连续分布的heusler相，且随Ti含量的增加，heusler相增多。热处理基本没有改变其合金的组织形貌，而含10Ti，12Ti的NiAl-Cr合金中heusler相随着热处理温度的提高而减少。加入Mo元素的铸态NiAl-Cr-Ti合金的组织组成没有变化，但共晶胞变小，Cr(Mo)相粗化，含10Ti，12Ti的NiAl-Cr(Mo)合金中heusler相仍存在于胞界处。吸铸态合金中的Cr(Mo)相，heusler相和共晶胞都得到了明显细化。铸态NiAl-Cr-1Zr合金由NiAl基体、Cr相以及胞界上不连续分布的Heusle（rNi2AlZr）相组成。随Zr含量的增加，heusler相增多。含Mo元素的铸态NiAl-Cr-Zr合金的组织组成没有变化，Mo元素的加入不影响heusler相的稳定性。热处理后，NiAl-Cr(Mo)-1Zr合金中的heusler相消失，而含2Zr或3Zr的NiAl-Cr(Mo)合金中heusler相随着热处理温度的提高而减少。铸态NiAl-Cr-5Co-1Zr合金为树枝晶组织，由NiAl基体、Cr相以及晶间处不连续分布的Heusle（rNi2AlZr）相和Al14Ni3Co3相组成。含10Co或15Co的铸态NiAl-Cr-Co-1Zr合金中没有heusler相，但有Al14Ni3Co3相。Co含量的增加，降低了heusler相的稳定性。热处理使NiAl-Cr-5Co-1Zr合金中的heusler相消失，但Al14Ni3Co3相仍存在。

关键词： NiAl heusler 吸铸显微组织相稳定性

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Half-metallic ferromagneticWeyl fermions related to dynamic correlations in the zinc-blende compound VAs

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CHINESE PHYSICS B 2024年第9期33卷 528-533页

作者： Ding, Xianyong Wei, Haoran Zhu, Ruixiang Xiao, Xiaoliang Wu, Xiaozhi Wang, Rui Chongqing Univ Inst Struct & Funct Chongqing 400044 Peoples R China Chongqing Univ Dept Phys Chongqing 400044 Peoples R China Chongqing Univ Chongqing Key Lab Strongly Coupled Phys Chongqing 400044 Peoples R China Chongqing Univ Ctr Quantum Mat & Devices Chongqing 400044 Peoples R China

The realization of 100% polarized topological Weyl fermions in half-metallic ferromagnets is of particular importance for fundamental research and spintronic applications. Here, we theoretically investigate the electronic and topological properties of the zinc-blende compound VAs, which was deemed as a half-metallic ferromagnet related to dynamic correlations. Based on the combination of density functional theory and dynamical mean field theory, we uncover that the half-metallic ferromagnet VAs exhibits attractive Weyl semimetallic behaviors which are very close to the Fermi level in the DFT + U regime with effect U values ranging from 1.5 eV to 2.5 eV. Meanwhile, we also investigate the magnetization-dependent topological properties; the results show that the change of magnetization directions only slightly affects the positions of Weyl points, which is attributed to the weak spin-orbital coupling effects. The topological surface states of VAs projected on semi-infinite (001) and (111) surfaces are investigated. The Fermi arcs of all Weyl points are clearly visible on the projected Fermi surfaces. Our findings suggest that VAs is a fully spin-polarized Weyl semimetal with many-body correlated effects in the effective U values range from 1.5 eV to 2.5 eV.

关键词： density functional theory Weyl semimetal dynamical mean field theory half metallic ferromagnet 71.55.Ak 71.15.Dx 75.50.Gg GROUND-STATE ENERGY ELECTRONIC-STRUCTURE WEYL heusler

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Critical behavior and magnetocaloric effect in magnetic Weyl semimetal candidate Co2-xZrSn

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Chinese Physics B 2019年第6期28卷 408-413页

作者： Tianlin Yu Xiaoyun Yu En Yang Chang Sun Xiao Zhang Ming Lei State Key Laboratory of Information Photonics and Optical Communications&School of Science Beijing University of Posts and Telecommunications

We investigate the critical exponents and magnetocaloric effect of Co2-xZrSn polycrystal. The Co2-xZrSn undergoes a second-order ferromagnetism phase transition around the Curie temperature of Tc ~280 K. The critical behavior in the vicinity of the magnetic phase transition has been investigated by using modified Arrott plot and Kouvel–Fisher *** obtained critical exponents, β, γ, and δ can be well described by the scaling theory. The determined exponents of Co2-xZrSn obey the mean-field model with a long-range magnetic interaction. In addition, the maximum magnetic entropy change-?Sm ax M of Co2-xZrSn is about 0.57 J·kg-1·K-1 and the relative cooling power(RCP) is 14.68 J·kg-1 at 50 kOe(1 Oe = 79.5775 A·m-1).

关键词： critical phenomena magnetocaloric effect heusler compound

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The unique magnetic damping enhancement in epitaxial Co2Fe1-xMnxAl films

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Chinese Physics B 2019年第9期28卷 332-337页

作者： Shu-Fa Li Chu-Yuan Cheng Kang-Kang Meng Chun-Lei Chen College of Electronics and Information Engineering Guangdong Ocean UniversityZhanjiang 524000China State-Key Laboratory of Optoelectronic Materials and Technologies School of PhysicsSun Yat-Sen UniversityGuangzhou 510275China State Key Laboratory for Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China

Uniform precession dynamics and its magnetic damping are investigated in epitaxial Co2Fe1-xMnxAl films by using the time-resolved magneto-optical Kerr effect under out-of-plane *** decay time of uniform precession mode decreases, and thus the magnetic damping increases with the increase of external ***, the decay time decreases as x decreases, so that the enhancement of magnetic damping occurs in Fe-rich ***, the decay time decreases as the excitation fluence increases, which drops rapidly at low magnetic field comparing with the slow reduction at high magnetic *** unique magnetic damping enhancement is attributed to the enhancement of homogeneous magnetization.

关键词： ultrafast dynamics pump-probe magnetic damping heusler alloy

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Influence of Magnetic Field Intensity on the Temperature Dependence of Magnetization of Ni2.08Mn0.96Ga0.96 Alloy

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Journal of Electromagnetic Analysis and Applications 2010年第7期2卷 431-435页

作者： Kharis Y. Mulyukov Irek I. Musabirov 不详

Results of investigation of the temperature dependence of magnetization of Ni2.08Mn0.96Ga0.96 alloy in the magnetic fields of various intensities are reported. An abrupt change in magnetization at transformation of low temperature phase to the high temperature one is observed. Magnetization increases during the phase transition in the magnetic field having intensity below 500 kA/m and decreases at higher intensities. The explanation is based on zigzag configuration of domains in twinned structure. In the Curie temperature region the ferromagnetic ? paramagnetic phase transition occurs sharply at low field strength, while at higher field strength the transition is smooth. It is concluded that the increase in flatness of the curve σ = f (T) and the increase of ferromagnetic state destruction temperature with increase of the intensity of the magnetic field is indicative of the main role of Mn in magnetization of the alloy.

关键词： Shape Memory Alloy Magnetization Ni-Mn-Ga Martensitic Transformation heusler Alloys

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Mn2基半金属材料能带结构调控的研究

Mn2基半金属材料能带结构调控的研究

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作者：盘如静重庆师范大学

学位级别：硕士

heusler合金自发现以来吸引了越来越多人们的关注,其丰富的物理特性和应用功能,使之成为了开发新型功能型材料的重要来源,在航空航天、计算机、医疗等领域有着巨大的运用价值。本文从第一性计算原理出发,基于密度泛函理论下,采用广义梯... 详细信息

heusler合金自发现以来吸引了越来越多人们的关注,其丰富的物理特性和应用功能,使之成为了开发新型功能型材料的重要来源,在航空航天、计算机、医疗等领域有着巨大的运用价值。本文从第一性计算原理出发,基于密度泛函理论下,采用广义梯度近似,对一系列掺杂后的合金进行理论研究,为实验提供理论依据。主要成果概括如下:1、对Mn32Co16-xFexSn16(0

关键词： heusler 合金半金属自旋无能隙半导体电子计数规则

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