Thickness-dependent magnetic structure of ultrathin Fe/Ir(001) films: From spin-spiral states toward ferromagnetic order
Thickness-dependent magnetic structure of ultrathin Fe/Ir(001) films: From spin-spiral states toward ferromagnetic order
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DOI：
10.1103/physrevb.84.224413
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发表时间：
2011-12-16
影响因子：
3.7
通讯作者：
Ujfalussy, B.
中科院分区：
文献类型：
--
作者：
Deak, A.;Szunyogh, L.;Ujfalussy, B.
本文对fcc Ir（001）表面超薄铁膜的基态磁性结构进行了详细的研究。我们将自旋簇展开技术与相对论无序局域矩格式相结合，得到了自旋模型的参数，然后通过平均场方法和原子自旋动力学模拟确定了系统的有利磁结构。对于单层铁，我们发现层弛豫对基态自旋构型有很强的影响，而Dzyaloshinskii-Moriya （DM）相互作用和双二次耦合也有显著的影响。为了描述后一种效应，我们引入并分析了系统的自旋共线性映射。由于DM相互作用，我们发现两层铁单分子层的自旋螺旋为基态，而对于四层铁单分子层，系统显示出非共线自旋结构和非零净磁化。这些发现与实验测量结果一致，表明四层或更厚的薄膜中铁磁有序。
We present a detailed study of the ground-state magnetic structure of ultrathin Fe films on the surface of fcc Ir(001). We use the spin-cluster expansion technique in combination with the relativistic disordered local moment scheme to obtain parameters of spin models and then determine the favored magnetic structure of the system by means of a mean-field approach and atomistic spin dynamics simulations. For the case of a single monolayer of Fe, we find that layer relaxations very strongly influence the ground-state spin configurations, whereas Dzyaloshinskii-Moriya (DM) interactions and biquadratic couplings also have remarkable effects. To characterize the latter effect, we introduce and analyze spin collinearity maps of the system. While for two monolayers of Fe we find a single-q spin spiral as ground state due to DM interactions, for the case of four monolayers, the system shows a noncollinear spin structure with nonzero net magnetization. These findings are consistent with experimental measurements indicating ferromagnetic order in films of four monolayers and thicker.