Microscopic Magnetic Origin of Rhombohedral Distortion in NiO

Abstract

Numerous investigations have been conducted to explore the structural phase transition in antiferromagnetic 3d transition metal monoxides accompanied by appearance of magnetic phase transition. However, how the spins induce distortion in the high symmetric structure has not yet been fully understood. In this study, the monoxide NiO is used as an example to investigate what lowers the structural symmetry. By comparing two different magnetic structures, our results reveal that the spin–lattice coupling is responsible for such a structural distortion. Then, a spin–lattice model, including the strain component, is constructed to simulate the transition procedure. Moreover, the results from the first-principles calculations are used to compare with our model results. Both first-principles calculations and model simulations clarify the structural phase transition caused by a unique magnetic arrangement.

Computational studies on magnetism and ferroelectricity

“…The polarization induced by the ion displacement u m and strain η j can also be computed with P α = Z αm u m + e α j η j , where Z αm and e α j are the Born effective charge and frozen-ion piezoelectric tensor, respectively. This unified model can not only describe the spin-lattice coupling in 2D CrI 3 , CrGeTe 3 [80] and monoxide NiO, [81] but also explain the ferroelectricity of the 2D multiferroic NiI 2 . [41]…”

“…The ion displacement and lattice deformation caused by the spin order can be obtained by minimizing the total energy E(um, ηj, Si) with respect to um and ηj, that is: and eαj are the Born effective charge and frozen-ion piezoelectric tensor, respectively. This unified model can not only describe the spin-lattice coupling in 2D CrI3, CrGeTe3 [80] and monoxide NiO, [81] but also explain the ferroelectricity of the 2D multiferroic NiI2. [41]…”