论文标题
RECO5中金属层中的高阶晶体场和稀土磁性
High-order crystal field and rare-earth magnetism in RECo5 intermetallics
论文作者
论文摘要
晶体场（CF）对铁磁间金属中的稀土离子的影响NDCO $ _5 $和TBCO $ _5 $通过与现场电子沟渠上的准原子近似相结合的均值近距离近似于sheltimation in sheltimed sheltiped seltsimed 4 $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $ f $。该研究揭示了CF的高阶部门谐波成分在RECO $ _5 $金属间的磁性中的重要作用。对于相应的晶体场参数（CFP）$ a_6^6 \ langle r^6 \ rangle $，在两个系统中都计算出一个出乎意料的大值，这远远超出了人们对仅静电贡献的期望。它允许在NDCO $ _5 $中沿Co Exchange字段中的零元素$ _5 $中的零温度和磁性矩解决零饱和的谜。以前已经从极化中子弹性散射探测的磁化分布中发现了这种不饱和状态，但理论上仍然无法解释。 NDCO $ _5 $中ND的易于平面电磁各向异性通过$ a_6^6 \ langle r^6 \ rangle $的巨大值强烈增强。违反直觉，易于平面内各向异性能量的极性依赖性仍然很小。 ND的易于平面电磁各向异性被加强到高温，这是通过$ J $混合效应来解释的。 NDCO $ _5 $及其温度依赖性的从头算量各向异性常数与实验定量一致。与ndco $ _5 $不同，$ a_6^6 \ langle r^6 \ rangle $ cfp对tbco $ _5 $中TB磁性的影响微不足道，这表明其对Re磁性的影响是Reco $ _5 $ _5 $系列的ION特定于ION特定的。其巨大价值的起源是在元素$ _5 $的金属层中，RE和CO州的杂交在六角形的当地环境中。
Crystal-field (CF) effects on the rare-earth (RE) ions in ferrimagnetic intermetallics NdCo$_5$ and TbCo$_5$ are evaluated using an ab initio density functional + dynamical mean-field theory approach in conjunction with a quasi-atomic approximation for on-site electronic correlations on the localized 4$f$ shell. The study reveals an important role of the high-order sectoral harmonic component of the CF in the magnetism of RECo$_5$ intermetallics. An unexpectedly large value is computed in the both systems for the corresponding crystal-field parameter (CFP) $A_6^6 \langle r^6 \rangle$, far beyond what one would expect from only electrostatic contributions. It allows solving the enigma of the non-saturation of zero-temperature Nd magnetic moments in NdCo$_5$ along its easy axis in the Co exchange field. This unsaturated state had been previously found out from magnetization distribution probed by polarised neutron elastic scattering but had so far remained theoretically unexplained. The easy plane magnetic anisotropy of Nd in NdCo$_5$ is strongly enhanced by the large value of $A_6^6\langle r^6 \rangle$. Counter-intuitively, the polar dependence of anisotropy energy within the easy plane remains rather small. The easy plane magnetic anisotropy of Nd is reinforced up to high temperatures, which is explained through $J$-mixing effects. The calculated ab initio anisotropy constants of NdCo$_5$ and their temperature dependence are in quantitative agreement with experiment. Unlike NdCo$_5$, the $A_6^6 \langle r^6 \rangle$ CFP has negligible effects on the Tb magnetism in TbCo$_5$ suggesting that its impact on the RE magnetism is ion-specific across the RECo$_5$ series. The origin of its large value is the hybridization of RE and Co states in a hexagonally coordinated local environment of the RE ion in RECo$_5$ intermetallics.
