The density of non-quasiparticle states in the ferrimagnetic full-Heuslers Mn$_2$VAl alloy is calculated from first principles upon appropriate inclusion of correlations. In contrast to most half-metallic compounds, this material displays an energy gap in the majority-spin spectrum. For this situation, non-quasiparticle states are located below the Fermi level, and should be detectable by spin-polarized photoemission. This opens a new way to study many-body effects in spintronic-related materials.
CeBi has an intricate magnetic phase diagram whose fully-polarized state has recently been suggested as a Weyl semimetal, though the role of $f$ states in promoting strong interactions has remained elusive. Here we focus on the less-studied, but also time-reversal symmetry-breaking ferrimagnetic phase of CeBi, where our density functional theory (DFT) calculations predict additional Weyl nodes near the Fermi level $E_\mathrm{F}$. We use spin-polarized scanning tunneling microscopy and spectroscopy to image the surface ferrimagnetic order on the itinerant Bi $p$ states, indicating their orbital…
Electron Correlations and the Minority-Spin Band Gap in Half-Metallic Heusler Alloys
电子-电子关联通过在费米能级之上引入非准粒子态来影响半金属铁磁体的带隙。与自旋轨道耦合不同，少数自旋通道中存在较大的非对称非准粒子谱权重，导致了特殊的有限温度自旋去极化效应。利用最近发展的第一性原理动力学平均场论，我们研究了半金属铁磁Heusler化合物FeMnSb的这些效应。讨论了FeMnSb中局部库仑相互作用$U$强度和温度对退极化效应的影响。我们提出了Ni $_{1-x}$ Fe $_{x}$ MnSb合金作为一种有前景的材料，用于自旋阀结构和半金属材料中的非准粒子态的实验研究。
Magnon-polarons are coherently mixed quasiparticles that originate from the strong magnetoelastic coupling of lattice vibrations and spin waves in magnetic-ordered materials. Recently, magnon-polarons have attracted a lot of attention since they provide a powerful tool to manipulate magnons, which is essential for magnon-based spintronic devices. In this work, we report the experimental observation of facet-dependent magnon-polarons in epitaxial ferrimagnetic Fe3O4 thin films via spin Seebeck effect measurement. The critical magnetic fields for the magnon-polarons in the (110)- and (100)-orien…
Spin, charge and orbital ordering in ferrimagnetic insulator YBaMn$_2$O$_5$
发现含有角连接MnO $_5$四棱锥的缺氧（双）钙钛矿型YBaMn $_2$ O $_5$在其基态表现出亚铁磁有序。在目前的工作中，我们报告广义梯度校正，相对论第一性原理全势能密度泛函计算进行YBaMn $_2$ O $_5$在的铁磁，铁磁和亚铁磁状态。的电荷，轨道和自旋的顺序解释与网站，角动量和轨道投影的状态密度，电荷密度图，电子结构和总能量的研究。YBaMn $_2$ O $_5$稳定在G型亚铁磁态。实验观察到的绝缘行为出现，只有当我们在我们的计算中包括亚铁磁有序。我们观察到显着的光学各向异性在这种材料中起源于亚铁磁有序和晶场分裂的综合效应。为了获得知识的存在下，不同的价态的锰在YBaMn $_2$ O $_5$，我们计算了$K$ -边的X射线吸收近边光谱的Mn和O原子。从X射线吸收近边谱、超精细场参数和磁性研究中可以清楚地确定Mn的不同价态的存在。在实验提出的结构中，最近报道的基于$P$ 4/ $nmm$的描述被发现代表稳定的结构。
Two-dimensional alternating ferrimagnetism with strain-controlled half-metallic state and valley polarization
School of Optoelectronic Engineering, Guangdong Polytechnic Normal University（广东技术师范大学光电工程学院）；Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials and Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University（华南师范大学南方先进光电子研究院量子工程与量子材料广东省重点实验室）；School of Physics, Hefei University of Technology（合肥工业大学物理学院）；Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University（东南大学物理学院教育部量子材料与器件重点实验室）
High TC fully compensated ferrimagnets are potential candidates for spin transfer torque based spintronic devices. We report the structural and magnetic properties of high TC fully compensated ferrimagnets Mn2V0.5Co0.5Z where Z is Ga, Al, in the melt spun ribbon and arc melted bulk form. While the parent alloys Mn2YZ where Y is V, Co and Z is Ga, Al exhibits a magnetic moment value around 2 muB per f.u, the Mn2V0.5Co0.5Ga alloy exhibits room temperature nearly fully compensated moment value of 0.09 and 0.13 muB per f.u. in the bulk and ribbon form respectively. For Mn2V0.5Co0.5Al this turned o…
We present a micromagnetic formulation for modeling the magnetization dynamics and thermal equilibrium in ferrimagnetic materials at low and elevated temperatures. The formulation is based on a mean field approximation (MFA). In this formulation, the ferrimagnet is described micromagnetically by two coupled sublattices with corresponding interactions, including inter- and intra-sublattice micromagnetic exchange as well as four-spin interactions described as an inter-sublattice molecular field with a cubic dependence of the magnetization. The MFA is used to derive a Landau Lifshitz Bloch type e…
Ferromagnetic materials dominate as the magnetically active element in spintronic devices, but come with drawbacks such as large stray fields, and low operational frequencies. Compensated ferrimagnets provide an alternative as they combine the ultrafast magnetization dynamics of antiferromagnets with a ferromagnet-like spin-orbit-torque (SOT) behavior. However to use ferrimagnets in spintronic devices their advantageous properties must be retained also in ultrathin films (t < 10 nm). In this study, ferrimagnetic Gdx(Fe87.5Co12.5)1-x thin films in the thickness range t = 2-20 nm were grown on h…
Magnetic Properties of a Quantum Ferrimagnet: NiCu(pba)(D_2O)_3 . 2D_2O
本文报道了NiCu（pba）（D_2O）_3PDMATHABMM 2D_2O $ (pba=1,3-propylenebis(oxamato)) which is one of the prototypical examples of an $ S $=1/2 and 1 ferrimagnetic chain. Susceptibility($ × $) shows a monotonous increase with decreasing temperature (T) and reaches a maximum at about 7 K. In the plot of $ × T $ versus $ T $, the experimental data exhibit a broad minimum and are fit to the $ × T $ curve calculated for the ferrimagnetic Heisenberg chain composed of S=1/2 and 1. From this fit, we have evaluated the nearest-neighbor exchange constant $ J/k_B=121 K $, the g-values of Ni$ ^{2 +} $ and Cu$ ^{2 +} …
Using ab initio calculations based on the correlated band theory, we have investigated the quasi-one-dimensional chain system $β$-V$_2$O(PO$_4$), showing both charge and spin orderings. Even in the uncorrelated region, the pure transition from the tetragonal to the monoclinic structure leads to a sizable charge difference between the two types of V ions, regardless of magnetic orders. In the ferrimagnetic phase, inclusion of the on-site Coulomb repulsion $U$ leads to a full orbital-polarization of V1 ($t_{2g}^{3\uparrow}$, $S=\frac{3}{2}$) and V2 ($a_{1g}^{1\downarrow}e_g^{\prime{1\downarrow}}…
Many technologically useful magnetic oxides are ferrimagnetic insulators, which consist of chemically distinct cations. Here, we examine the spin dynamics of different magnetic cations in ferrimagnetic NiZnAl-ferrite (Ni$_{0.65}$Zn$_{0.35}$Al$_{0.8}$Fe$_{1.2}$O$_4$) under continuous microwave excitation. Specifically, we employ time-resolved x-ray ferromagnetic resonance to separately probe Fe$^{2+/3+}$ and Ni$^{2+}$ cations on different sublattice sites. Our results show that the precessing cation moments retain a rigid, collinear configuration to within $\approx$2$^\circ$. Moreover, the effe…
It has been shown that W in its resistive form possesses the largest spin-Hall ratio among all heavy transition metals, which makes it a good candidate for generating efficient dampinglike spin-orbit torque (DL-SOT) acting upon adjacent ferromagnetic or ferrimagnetic (FM) layer. Here we provide a systematic study on the spin transport properties of W/FM magnetic heterostructures with the FM layer being ferromagnetic Co$_{20}$Fe$_{60}$B$_{20}$ or ferrimagnetic Co$_{63}$Tb$_{37}$ with perpendicular magnetic anisotropy. The DL-SOT efficiency $|ξ_{DL}|$, which is characterized by a current-induced…
Compensated ferrimagnets, like antiferromagnets, show no net magnetization but their transport and magneto-optic properties resemble those of ferromagnets, thereby creating opportunities for applications in high-frequency spintronics and low-energy loss communications. Here we study the modification the noncollinear ferrimagnetic spin structure of Mn4N by a variety of metallic substitutions Z (Z = Cu - Ge and Ag - Sn) to achieve compensation at room temperature. The noncollinear frustrated 2.35 Bohr magneton moments of Mn on 3c sites of the (111) kagome planes tilt about 20 degree out-of-plane…
Magnetic skyrmions are swirling magnetic textures that can be efficiently driven with spin-orbit torques with a deflected trajectory. However, pinning slows skyrmions down and alters their trajectory, which prevents a quantitative comparison to analytical models. Here, we study skyrmions driven by spin-orbit torques at room temperature in ferrimagnetic GdCo thin films, an amorphous material with low pinning. Above a sharp current depinning threshold, we observe a clearly linear velocity increase with current that extrapolates to zero and a constant deflection angle, reaching high velocities up…
The anomalous Nernst effect (ANE), a heat-charge conversion mechanism based on a magnetic metal, has been extensively studied for application in thin thermoelectric devices. The low magnetization and fabrication at room temperature are important for flexible ANE thermoelectric devices on plastic substrates. Therefore, we investigated the ANE in ferrimagnetic GdxFe100-x films with low magnetization in this study by systematically varying the Gd composition x. Although the Gd33Fe67 film with a Gd composition close to magnetic compensation composition exhibited very low magnetization, an ANE coef…
Electronic structure and magnetic properties of Fe$_3$Se$_4$ are calculated using the density functional approach. Due to the metallic properties, magnetic moments of the iron atoms in two nonequivalent positions in the unit cell are different from ionic values for Fe$^{3+}$ and Fe$^{2+}$ and are equal to $M_1=2.071 μ_B$ and $M_2=-2.042 μ_B$, making the system ferrimagnetic. The total magnetic moment for the unit cell is $2.135 μ_B$. Under isotropic compression, the total magnetic moment decreases non-monotonically and correlates with the non-monotonic dependence of the density of states at th…
Spin-flop transition (SFT) consists in a jump-like reversal of antiferromagnetic magnetic moments into a non-collinear state when the magnetic field increases above the critical value. Potentially the SFT can be utilized in many applications of a rapidly developing antiferromagnetic spintronics. However, the difficulty of using them in conventional antiferromagnets lies in (a) too large switching magnetic fields (b) the need for presence of a magnetic anisotropy, and (c) requirement to apply magnetic field along the correspondent anisotropy axis. In this work we propose to use artificial ferri…
We synthesized a pure organic non-metal crystalline covalent organic framework TAPA-BTD-COF by bottom-up Schiff base chemical reaction. And this imine-based COF is stable in aerobic condition and room-temperature. We discovered that this TAPA-BTD-COF exhibited strong magneticity in 300 K generating magnetic hysteresis loop in M-H characterization and giant chimol up to 0.028. And we further conducted zero-field cooling and field-cooling measurement of M-T curves. The as-synthesized materials showed a large chi/mol up to 0.028 in 300 K and increasing to 0.037 in 4.0 K with 200 Oe measurement fi…
Geometry-Driven Magnetoelectric Coupling in Two-Dimensional Compensated Ferrimagnets
School of Emerging Technology and Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China（中国科学技术大学新兴技术学院与微观物质科学国家研究中心）；State Key Laboratory of Precision and Intelligent Chemistry, School of Chemistry and Materials Science, and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), University of Science and Technology of China（中国科学技术大学精密与智能化学国家重点实验室、化学与材料科学学院及能源材料化学协同创新中心）；Hefei National Laboratory, University of Science and Technology of China（中国科学技术大学合肥国家实验室）
We performed first-principles density functional theory (DFT) and GW calculations to investigate electronic structures of bulk and few-layer PdSe2. We obtained the quasiparticle band structure of bulk PdSe2, and the obtained energy gap agrees excellently with the reported experimental value. For monolayer and bilayer PdSe2, we obtained quasiparticle band structures with respect to the vacuum level. We analyzed DFT and GW band structures in detail, finding k-space positions of valence band maxima and conduction band minima, effective masses, the quasiparticle density of states, work functions, …
