Fritsch Daniel
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.
J Phys Condens Matter. 2018 Mar 7;30(9):095502. doi: 10.1088/1361-648X/aaa7c5.
Spinel ferrites in general show a rich interplay of structural, electronic, and magnetic properties. Here, we particularly focus on zinc ferrite (ZFO), which has been observed experimentally to crystallise in the cubic normal spinel structure. However, its magnetic ground state is still under dispute. In addition, some unusual magnetic properties in ZFO thin films or nanostructures have been explained by a possible partial cation inversion and a different magnetic interaction between the two cation sublattices of the spinel structure compared to the crystalline bulk material. Here, density functional theory has been applied to investigate the influence of different inversion degrees and magnetic couplings among the cation sublattices on the structural, electronic, magnetic, and optical properties. Effects of exchange and correlation have been modelled using the generalised gradient approximation (GGA) together with the Hubbard '+U' parameter, and the more elaborate hybrid functional PBE0. While the GGA+U calculations yield an antiferromagnetically coupled normal spinel structure as the ground state, in the PBE0 calculations the ferromagnetically coupled normal spinel is energetically slightly favoured, and the hybrid functional calculations perform much better with respect to structural, electronic and optical properties.
一般来说，尖晶石铁氧体呈现出结构、电子和磁性之间丰富的相互作用。在这里，我们特别关注锌铁氧体（ZFO），实验观察到它以立方正常尖晶石结构结晶。然而，其磁基态仍存在争议。此外，与晶体块状材料相比，ZFO薄膜或纳米结构中的一些异常磁性已通过可能的部分阳离子反位以及尖晶石结构的两个阳离子亚晶格之间不同的磁相互作用来解释。在这里，密度泛函理论已被用于研究阳离子亚晶格之间不同的反位程度和磁耦合对结构、电子、磁性和光学性质的影响。使用广义梯度近似（GGA）以及哈伯德“+U”参数对交换和关联效应进行了建模，并采用了更精细的杂化泛函PBE0。虽然GGA+U计算得出反铁磁耦合的正常尖晶石结构作为基态，但在PBE0计算中，铁磁耦合的正常尖晶石在能量上略占优势，并且杂化泛函计算在结构、电子和光学性质方面表现得更好。
