Mishra Priyanka, Autieri Carmine
International Research Centre Magtop, Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland.
Molecules. 2024 Dec 5;29(23):5751. doi: 10.3390/molecules29235751.
We present first-principles results on the electronic and magnetic properties of the cubic bulk β-phase of Fe2O3. Given that all Fe-Fe magnetic couplings are expected to be antiferromagnetic within this high-symmetry crystal structure, the system may exhibit some signature of magnetic frustration, making it challenging to identify its magnetic ground state. We have analyzed the possible magnetic phases of the β-phase, among which there are ferrimagnets, altermagnets, and Kramers antiferromagnets. While the α-phase is an altermagnet and the γ-phase is a ferrimagnet, we conclude that the magnetic ground state for the bulk β-phase of Fe2O3 is a Kramers antiferromagnet. Moreover, we find that close in energy, there is a bulk d-wave altermagnetic phase. We report the density of states and the evolution band gap as a function of the electronic correlations. For suitable values of the Coulomb repulsion, the system is a charge-transfer insulator with an indirect band gap of 1.5 eV. More in detail, the unit cell of the β-phase is composed of 8Fea atoms and 24Feb atoms. The 8Fea atoms lie on the corner of a cube, and their magnetic ground state is a G-type. This structural phase is composed of zig-zag chains Fea-Feb-Fea-Feb with spin configuration ↑-↑-↓-↓ along the 3 directions such that for every Fea atoms there are 3Feb atoms. As the opposite to the γ-phase, the magnetic configuration between the first neighbor of the same kind is always antiferromagnetic while the magnetic configuration between Fea and Feb is ferro or antiferro. In this magnetic arrangement, first-neighbor interactions cancel out in the mean-field estimation of the Néel temperature, leaving second-neighbor magnetic exchanges as the primary contributors, resulting in a Néel temperature lower than that of other phases. Our work paves the way toward the ab initio study of nanoparticles and alloys for the β-phase of Fe2O3.
我们展示了关于立方块状β相Fe₂O₃的电子和磁性性质的第一性原理结果。鉴于在这种高对称晶体结构中所有Fe-Fe磁耦合预计都是反铁磁性的，该系统可能表现出一些磁阻挫的特征，这使得确定其磁基态具有挑战性。我们分析了β相可能的磁相，其中包括亚铁磁体、交替磁体和克莱默斯反铁磁体。虽然α相是交替磁体而γ相是亚铁磁体，但我们得出结论，块状β相Fe₂O₃的磁基态是克莱默斯反铁磁体。此外，我们发现能量相近处存在一个块状d波交替磁相。我们报告了态密度以及作为电子关联函数的能带隙演化。对于合适的库仑排斥值，该系统是一种电荷转移绝缘体，间接带隙为1.5 eV。更详细地说，β相的晶胞由8个Fea原子和24个Feb原子组成。8个Fea原子位于立方体的角上，它们的磁基态是G型。这个结构相由之字形链Fea-Feb-Fea-Feb组成，沿3个方向的自旋构型为↑-↑-↓-↓，使得每个Fea原子有3个Feb原子。与γ相相反，同类最近邻之间的磁构型总是反铁磁性的，而Fea和Feb之间的磁构型是铁磁性或反铁磁性的。在这种磁排列中，最近邻相互作用在奈尔温度的平均场估计中相互抵消，使得次近邻磁交换成为主要贡献者，导致奈尔温度低于其他相。我们的工作为对Fe₂O₃的β相纳米颗粒和合金进行从头算研究铺平了道路。
