Gd2Co2Al电子结构和磁性的第一性原理研究

从第一性原理出发，在局域自旋密度近似(LSDA)和LSDA+U(在位库仑能)近似下，采用FPLAPW密度泛函能带计算方法研究了Gd₂Co₂Al的电子结构和磁性. 从平均场近似出发，估算了体系的居里温度，并分析了导致体系居里温度偏低的原因.研究结果显示Gd₂Co₂Al为金属导体，其强的铁磁性的提供者主要是Gd，且Co的局域铁磁性是不稳定的. 基于LSDA近似的计算表明Gd₂Co₂关键词： 稀土过渡族金属间化合物 密度泛函理论 电子结构 磁性性质

First-principles calculations of electronic structure and magnetism of Gd2Co2Al

We investigate the electronic and magnetic properties of the new compound Gd₂Co₂Al by using a self-consistent full-potential linearized augmented plane-wave method within the local spin-density approximation (LSDA) and the LSDA+U approximation to the exchange-correlation potential of the spin-density functional theory. We have also discussed the reason of system to have low Curie temperature, and made use of the average field theory to calculate the Curie temperature in combination with the results of density functional calculation. Our calculation shows that this system is a metallic conductor. The local Gd magnetic moment provides predominately the strong ferromagnetism and the Co-site local moment is unstable. Gd₂Co₂Al is shown to be a ferrimagnetic phase due to the moment of Gd sublattice being aligned antiparallelly to the Co moment in the LSDA. After considering the on-site Coulomb interaction by an additional Hubbard parameter U, it is found that the ground state becomes ferromagnetic at a moderate value of U (3.0eV), with a Co ion magnetic moment of 0.024μ_B, which is in good agreement with experiment. The moment of Co changes much and the density of states of Gd and Co are significantly redistributed with the change of U, while the magnetic moment of Gd does not change much. The competition of 5d-3d hybridization and the on-site Coulomb interaction leads to the fluctuation of the moment of Co.