Effect of structure on the magnetic anisotropy of L 1 0 FePt nanoparticles
Effect of structure on the magnetic anisotropy of L 1 0 FePt nanoparticles
复制标题
DOI：
10.1103/physrevb.92.054424
复制
发表时间：
2014-09
影响因子：
3.7
通讯作者：
A. Kabir;Jun Hu;V. Turkowski;R. Wu;T. Rahman
中科院分区：
文献类型：
--
作者：
A. Kabir;Jun Hu;V. Turkowski;R. Wu;T. Rahman
我们对Fe和Pt面沿着（001）方向交替排列的L10 FePt团簇的磁晶各向异性（MCA）进行了系统的理论研究。我们用从头算自旋极化密度泛函理论（DFT）计算了每个团簇的结构弛豫和磁矩，并用自旋极化密度泛函理论（包括自旋轨道耦合自洽）和矩方法计算了每个团簇的结构弛豫和磁矩.我们发现，MCA的任何复合结构的一个给定的大小是增强相对于相同大小的纯Pt或纯Fe集群，以及任何对的Fe和Pt原子在散装L10 FePt。这种增强的结果，我们观察到的Fe原子的3d轨道和它们的Pt邻居的5d轨道之间的杂化。然而，这种杂化以显著不同的方式影响组成原子的电子性质。虽然它在一定程度上增加了Fe原子的自旋矩，但对它们的轨道矩几乎没有影响;同时，它大大增加了Pt原子的自旋和轨道矩。考虑到Pt的自旋-轨道耦合（SOC）常数比Fe的大约7倍的事实，这种Fe诱导的Pt原子的轨道矩的跳跃产生复合结构的MCA相对于它们的纯对应物的MCA的增加。任何复合结构都具有比体L10 FePt更高的MCA，这是由于团簇中Pt原子的配位较低，无论是Fe还是Pt占主导地位。我们还发现，中心层为Pt的双锥团簇具有比相同尺寸的中心层为Fe的双锥团簇更高的MCA。这是由于这样的配置中的Pt原子与比后者中更多的Fe原子配位的事实。通过参与更多的杂交，它们对单位的整体MCA贡献更高的轨道矩。
We carry out a systematic theoretical investigation of Magneto Crystalline Anisotropy (MCA) of L10 FePt clusters with alternating Fe and Pt planes along the (001) direction. We calculate the structural relaxation and magnetic moment of each cluster by using ab initio spin-polarized density functional theory (DFT), and the MCA with both spin-polarized DFT (including spin-orbit coupling self-consistently) and the torque method. We find that the MCA of any composite structure of a given size is enhanced with respect to that of the same-sized pure Pt or pure Fe cluster as well as to that of any pair of Fe and Pt atoms in bulk L10 FePt. This enhancement results from the hybridization we observe between the 3d orbital of the Fe atoms and the 5d orbital of their Pt neighbors. This hybridization, however, affects the electronic properties of the component atoms in significantly different ways. While it somewhat increases the spin moment of the Fe atoms, it has little effect on their orbital moment; at the same time, it greatly increases both the spin and orbital moment of the Pt atoms. Given the fact that the spin-orbit coupling (SOC) constant of Pt is about 7 times greater than that of Fe, this Fe-induced jump in the orbital moment of the Pt atoms produces the increase in MCA of the composite structures over that of their pure counterparts. That any composite structure exhibits higher MCA than bulk L10 FePt results from the lower coordination of Pt atoms in the cluster, whether Fe or Pt predominates within it. We also find that bipyramidal clusters whose central layer is Pt have higher MCA than their same-sized counterparts whose central layer is Fe. This results from the fact that Pt atoms in such configurations are coordinated with more Fe atoms than in the latter. By thus participating in more instances of hybridization, they contribute higher orbital moments to the overall MCA of the unit.