论文标题
第一原则研究立方GDCU化合物的电子和磁性
First-principles study of the electronic and magnetic properties of cubic GdCu compound
论文作者
论文摘要
使用旋转密度功能理论研究了大量GDCU(CSCL型)的结构,电子和磁性,其中在LDA+$ u $和GGA+$ u $方法中处理了高度局部$ 4F $轨道。使用共线以及自旋螺旋计算的GDCU计算出的磁接地状态表现出C型反铁磁性构型,代表了自旋螺旋传播矢量$ \ MATHBF {q} = \ frac {2π} {2π} {a} {a} {a}(\ frac {\ frac {1} {1} {2} {2} {2从自洽的电子结构中评估有效的Heisenberg Hamiltonian的参数,并用于确定磁过渡温度。使用GGA+$ U $和LDA+$ U $密度函数在平均字段和随机相位近似值内使用GGA+$ U $和LDA+$ U $密度函数的估计的Néel温度与实验测量值非常吻合。特别是,对实验观察到的核心GD $ 4F $水平的理论理解进行了详细研究。通过采用自洽约束随机相近似,我们确定了本地化$ 4F $电子之间有效库仑相互作用(Hubbard $ u $)的强度。我们发现,GD-$ 4F $状态在GDCU中相对于DFT+$ U $内的批量GD的偏移对晶格参数的选择敏感。使用DFT+$ U $方法以及Hubbard-1近似的$ 4F $级别的计算与实验发现不一致。
The structural, electronic, and magnetic properties of bulk GdCu (CsCl-type) are investigated using spin density functional theory, where highly localized $4f$ orbitals are treated within LDA+$U$ and GGA+$U$ methods. The calculated magnetic ground state of GdCu using collinear as well as spin spiral calculations exhibits a C-type antiferromagnetic configuration representing a spin spiral propagation vector $\mathbf{Q}=\frac{2π}{a}(\frac{1}{2},\frac{1}{2},0)$. The parameters of the effective Heisenberg Hamiltonian are evaluated from a self-consistent electronic structure and are used to determine the magnetic transition temperature. The estimated Néel temperature of the cubic GdCu using GGA+$U$ and LDA+$U$ density functionals within the mean field and random phase approximations are in good agreement with the experimentally measured values. In particular, the theoretical understanding of the experimentally observed core Gd $4f$ levels shifting in photoemission spectroscopy experiments is investigated in detail. By employing the self-consistent constrained random-phase approximation we determined the strength of the effective Coulomb interaction (Hubbard $U$) between localized $4f$ electrons. We find that, the shift of Gd-$4f$ states in GdCu with respect to bulk Gd within DFT+$U$ is sensitive to choice of lattice parameter. The calculations for $4f$-level shifts using DFT+$U$ methods as well as Hubbard-1 approximation are not consistent with the experimental findings.