Dzyaloshinskii-Moriya-type interaction and Lifshitz invariant in Rashba 2D electron gas systems

The origin of chiral magnetic structures in ultrathin films of magnetic metals is analyzed. It is shown that the Lifshitz-type invariant term in the macroscopic thermodynamic potential can be derived from spin-orbit Rashba Hamiltonian in two dimensional electron gas (2DEG). The former is the prerequisite for existence of spin cycloid, skyrmions and other chiral phenomena observed in thin films. The estimation of the period of spin cycloid gives the value of an order of 10 nm that agrees well with the results of scanning probe microscopy observation reported in the literature

The curvature-induced magnetization in CrI3 bilayer: flexomagnetic effect enhancement in van der Waals antiferromagnets

The bilayer of CrI3 is a prototypical van der Waals 2D antiferromagnetic material with magnetoelectric effect. It is not generally known, however, that for symmetry reasons the flexomagnetic effect, i.e., the strain gradient-induced magnetization, is also possible in this material. In the present paper, based on the first principle calculations, we estimate the flexomagnetic effect to be 200 {\mu}B{\AA} that is two orders of magnitude higher than it was predicted for the referent antiperovskite flexomagnetic material Mn3GaN. The two major factors of flexomagnetic effect enhancement related to the peculiarities of antiferromagnetic structure of van der Waals magnets is revealed: the strain-dependent ferromagnetic coupling in each layer and large interlayer distance separating antiferromagnetically coupled ions. Since 2D systems are naturally prone to mechanical deformation, the emerging field of flexomagnetism is of special interest for application in spintronics of van der Waals materials and straintronics in particular

On the problem of coexistence of the weak ferromagnetism and the spin flexoelectricity in multiferroic bismuth ferrite

On the example of the prototypical multiferroic bismuth ferrite the microscopic origin of the spin flexoelectricity responsible for the spin cycloid ordering is analyzed. It is shown how the three basic structural distortions corresponding to the frozen-phonon modes of an ideal perovskite lattice result in the coexistence of the spin canting and the spin cycloidal ordering. On the basis of a simple formula for the antisymmetric Dzyaloshinskii-Moriya superexchange the inhomogenous magnetoelectric contribution to the theromodynamic potential is derived and the values of the microscopic parameters corresponding to the spin canting and the spin cycloid are determined

The electric-field–induced “zero-degree domain walls” in ferromagnets

The internal structure of electric-field–induced magnetic topological defects in dielectric magnetic film with inhomogeneous magnetoelectric effect is considered. It is shown that this “zero-degree domain wall” has a complex internal structure with the sense of magnetization rotation and corresponding electric polarity changing twice across the wall. The two possible solutions corresponding to 0° domain walls (the pure cycloidal domain wall and the mixed one) as well as their energies are analyzed. It is shown that the 0° domain wall is a transitional state between the homogeneously magnetized media and the electric-field–induced magnetic domain. The critical field of the domain nucleation obtained from this model is within the range of experimental values of several MV/cm