Ab initio theory of exchange interactions and the Curie temperature of bulk Gd
Ab initio theory of exchange interactions and the Curie temperature of bulk Gd
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DOI：
10.1088/0953-8984/15/17/327
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发表时间：
2003-05-07
影响因子：
2.7
通讯作者：
Blügel, S
中科院分区：
文献类型：
--
作者：
Turek, I;Kudrnovsky, J;Blügel, S
在局域自旋密度近似下，将4f电子作为局域核电子，用从头算方法研究了大块六方晶系Gd的磁性.在原子球近似下，用紧束缚线性Muffin-tin轨道方法求解有效单电子问题，价基由s-、p-和d-型轨道组成。该方法导致一个正确的描述的基态性质，如铁磁结构的稳定性，磁矩和平衡晶格常数。应用一个真实的空间格林函数形式主义产生的交换对之间的相互作用，是不可避免的定量研究磁激发的遥远的邻居。交换对相互作用的距离依赖性和各向异性，并在平均场近似下的居里温度进行评估。得到的334 K值与293 K的实验值比以前的理论结果更好地吻合。取决于原子体积，我们发现一个非常大的依赖的居里温度的C/A比，这承担着重要的后果厚应变Gd膜生长在各种衬底上的临界温度。
An ab initio approach to the magnetic properties of bulk hexagonal Gd is developed that is based on the local spin-density approximation with the 4f electrons treated as localized core electrons. The effective one-electron problem is solved using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation with the valence basis consisting of s-, p- and d-type orbitals. The approach leads to a correct description of the ground-state properties like the stability of the ferromagnetic structure, the magnetic moment and the equilibrium lattice constant. Application of a real-space Green-function formalism yields the exchange pair interactions between distant neighbours that are inevitable for quantitative studies of magnetic excitations. The distance dependence and anisotropy of the exchange pair interactions are presented and the Curie temperature in the mean-field approximation is evaluated. The obtained value of 334 K is in much better agreement with the experimental value of 293 K than previous theoretical results. Depending on the atomic volume we find an unusually large dependence of the Curie temperature on the c/a ratio, which bears important consequences for the critical temperatures of thick strained Gd films as grown on various substrates.