Phase-field simulation of strain-induced domain switching in magnetic thin films

Abstract

The strain-induced magnetic domain switching in epitaxial CoFe2O4 (CFO) thin films was studied using phase-field method. In particular, we investigated the domain switching from an initial in-plane direction to out-of-plane under the action of in-plane elastic strains. An abrupt switching feature is observed for a single-domain film while the switching of a multidomain CFO thin film is gradual. Typical magnetic domain structures as a result of the biaxial isotropic in-plane strains are presented.

Electrically controlled non-volatile switching of magnetism in multiferroic heterostructures via engineered ferroelastic domain states

“…58 Note that the use of average strain as the model input is reasonable only when the average size of one single magnetic domain in the FeGaB film is sufficiently large to cover many of the ferroelectric domains on the PMN-PT surface, otherwise one may use the nominal domain switching-induced lattice deformation as the input. Starting from random magnetization distribution, an almost uniform magnetization distribution is obtained at equilibrium under zero strain, and is further evolved to new equilibrium state upon applying the strain transferred from the PMN-PT substrate.…”

Film size-dependent voltage-modulated magnetism in multiferroic heterostructures

“…In general, a precise control over the domain (wall) patterns (e.g. via strain [57,94] or topological defects [95]) is essential to device applications. Specifically, how do we understand the influence of the FE domain (ferroelastic) switching on both the static magnetic domain (wall) morphology and its dynamic evolution process?…”

“…see the circle 2 in figure 4d) under a positive in-plane strain ε 0 of 0.3%. Note that even local 180 • Ising-type-like wall is observed (see the circle 1 in figure 4d) owing to the relative strong elastic energy which can significantly narrow down the domain-wall length [57]. On the other hand, the film would display an in-plane multi-domain structure with a vortex-type 180 • Néel wall (see the circle 3 in figure 4d) under a negative ε 0 of −0.3%.…”

“…the length and width, assumed to be equal herein) of the magnetic film would also exert significant influence on the domain states as a result of the competing exchange and magnetostatic energy [79,80], for example, the film would display a uniform single-domain structure at small sizes owing to the dominative exchange anisotropy, whereas it would be in a multi-domain state at large sizes in order to reduce the magnetostatic energy. These domain structures would lead to different voltage-induced magnetizationswitching characteristics accordingly [57,58], which is critical to the potential device application [59,60]. Here, we use a phase-field model [81][82][83] to investigate such lateral size-dependent voltage manipulation of magnetization.…”

“…For illustration, figure 4a shows the isotropic strain-induced out-of-plane magnetization switching in a highly magnetostrictive (001) CoFe 2 O 4 (CFO) film of 64 × 64 × 18 nm 3 [57]. Such isotropic strain ε 0 can be obtained either from the intrinsic lattice and/or thermal mismatch between a film and a substrate [84] or from external piezoelectric actuation [85].…”