Laves相Fe $_2$ Ta $_{1-x}$ W $_x$磁晶各向异性的第一性原理研究--3d-5d杂化效应
Magnetocrystalline anisotropy of Laves phase Fe$_2$Ta$_{1-x}$W$_x$ from first principles - the effect of 3d-5d hybridisation
摘要：
采用密度泛函理论，在广义梯度近似下，用全势线性缀加平面波方法计算了六方Laves相Fe $_2$ Ta和Fe $_2$ W的磁性.用虚晶近似处理无序，研究了Fe $_2$ Ta $_{1-x}$ W $_x$合金. Fe $_2$ Ta被发现是铁磁性的，饱和磁化强度为$μ_0 M_\text{s} = 0.66~\mathrm{T}$，而与早期的计算工作相比，Fe $_2$ W被发现是亚铁磁性的，具有$μ_0 M_\text{s} = 0.35~\mathrm{T}$。对于$x \leq 0.1$，发生从铁态到铁磁态的转变。计算了Fe $_2$ Ta的磁晶各向异性能（MAE）为$1.25~\mathrm{MJ/m^3}$，Fe $_2$ W的磁晶各向异性能为$0.87~\mathrm{MJ/m^3}$.发现对于Fe $_2$ Ta $_{1-x}$ W $_x$中的所有值$x$，MAE都小于末端化合物，并且对于$0.1 \leq x \leq 0.9$，MAE为负（面内各向异性）。的MAE仔细分析的电子结构。即使有弱的5d贡献的状态密度在费米能在两端的化合物，倒易空间分析，使用磁力定理，揭示了MAE主要来自区域的布里渊区附近的费米能与强大的3d-5d杂化。微扰理论及其适用性的MAE进行了讨论。
英文摘要：
The magnetic properties of Fe$_2$Ta and Fe$_2$W in the hexagonal Laves phase are computed using density functional theory in the generalised gradient approximation, with the full potential linearised augmented plane wave method. The alloy Fe$_2$Ta$_{1-x}$W$_x$ is studied using the virtual crystal approximation to treat disorder. Fe$_2$Ta is found to be ferromagnetic with a saturation magnetization of $μ_0 M_\text{s} = 0.66~\mathrm{T}$ while, in contrast to earlier computational work, Fe$_2$W is found to be ferrimagnetic with $μ_0 M_\text{s} = 0.35~\mathrm{T}$. The transition from the ferri- to the ferromagnetic state occurs for $x \leq 0.1$. The magnetocrystalline anisotropy energy (MAE) is calculated to $1.25~\mathrm{MJ/m^3}$ for Fe$_2$Ta and $0.87~\mathrm{MJ/m^3}$ for Fe$_2$W. The MAE is found to be smaller for all values $x$ in Fe$_2$Ta$_{1-x}$W$_x$ than for the end compounds and it is negative (in-plane anisotropy) for $0.1 \leq x \leq 0.9$. The MAE is carefully analysed in terms of the electronic structure. Even though there are weak 5d contributions to the density of states at the Fermi energy in both end compounds, a reciprocal space analysis, using the magnetic force theorem, reveals that the MAE originates mainly from regions of the Brillouin zone with strong 3d-5d hybridisation near the Fermi energy. Perturbation theory and its applicability in relation to the MAE is discussed.
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