General microscopic model of magnetoelastic coupling from first principles

Abstract

Magnetoelastic coupling, i.e., the change of crystal lattice induced by a spin order, is not only scientifically interesting, but also technically important. In this work, we propose a general microscopic model from first-principles calculations to describe the magnetoelastic coupling and provide a way to construct the microscopic model from density functional theory calculations.Based on this model, we reveal that there exists a previously unexpected contribution to the electric polarization induced by the spin-order in multiferroics due to the combined effects of magnetoelastic coupling and piezoelectric effect. Interestingly and surprisingly, we find that this lattice deformation contribution to the polarization is even larger than that from the pure electronic and ion-displacement contributions in BiFeO3. This model of magnetoelastic coupling can be generally applied to investigate the other magnetoelastic phenomena. 75.80.+q, 75.85.+t, 71.15.-m, 77.65.-j PACS:

Spin-induced polarizations and nonreciprocal directional dichroism of the room-temperature multiferroicBiFeO3

“…A unified model of ferroelectricity 55,56 also concludes that SC and ANI make minor contributions to P ind compared to MS. The distinction between static and dynamics properties in BiFeO 3 is not surprising.…”

Microscopic mechanism of spin-order induced improper ferroelectric polarization

“…The polarization induced by the helical spin order in MnI 2 [33] can be well explained by the general spin current term. In BiFeO 3 [30], the pure electronic, ion displacement, and lattice deformation contributions are of comparable magnitude.…”

“…And some experimental results (such as ferroelectric polarization induced by proper screw spin order) could not be explained by previous models. Recently, we [29][30][31][32][33][34] develop a unified model for spin order induced improper ferroelectric polarization of multiferroics. This unified model can explain the polarization induced by any spin structures: collinear, cycloidal spiral, proper screw, etc.…”

“…Schematic illustration of three contributions to the electric polarization induced by a spin order in multiferroics [30]. In all known systems, the anisotropic symmetric term P !…”

“…Some phenomenological theories based on symmetry analysis have also been built to describe the coupling between spin order and ferroelectric polarization [28]. More recently, we [29][30][31][32][33][34] established a unified model for the microscopic mechanism of spin-order induced ferroelectricity in multiferroics, which includes the pure electronic, ion displacement and lattice deformation contributions. It should be noted that in type-I multiferroics, there may also exist spin-order induced polarization and the model is also applicable.…”