Role of magnetostatic interactions in micromagnetic structure of multiferroics

Abstract

While it is well known that magnetoelastic coupling governs the magnitude of field-induced strain in magnetic shape memory alloys, the present study shows that the zero-field micromagnetic structure and the pathway leading to the field-induced strain is governed by magnetostatic coupling across martensite twins. The micromagnetic investigations reveal a new energy barrier to the motion of domain walls arising from magnetostatic coupling between walls across the twin planes.

In situ lorentz TEM magnetization study of a Ni–Mn–Ga ferromagnetic shape memory alloy

“…A possible reason for such a contradiction in the observations may be the difference in specimen thickness (4.5 mm in case of Lai's study vs. %100 nm in our study). It is worthwhile noting that Armstrong et al [13] also observed the movement of 180°walls within the twin variants of a Co-Ni-Ga crystal with a thickness of 0.89 mm. Theoretical models concerning the movement of domain walls in soft magnetic alloys point out that eddy current effects can dampen the domain wall motion in the case of thicker samples [23]; this may explain the discrepancies between these observations.…”

“…This may be related to how the magnetostatic coupling between twin variants influences the domain wall motion. Armstrong et al [13] observed domain wall motion in a twinned crystal of a Co-Ni-Ga alloy under the application of a magnetic field. They reported that the magnetostatic coupling across twin variants can act as an energy barrier, increasing the resistance to domain wall motion.…”

“…The sample coercivity was attributed to pinning of domain walls at the twin boundaries. In a recent study, Armstrong et al reported that the magnetostatic coupling between domains belonging to adjacent twins can give rise to an energy barrier to the motion of domain walls under an applied magnetic field [13]. It should be noted that the martensitic microstructures in MSMAs can contain extremely fine twin variants (ranging from a few nm to a few lm).…”

Magnetic-Field-Induced Effects in Martensitic Heusler-Based Magnetic Shape Memory Alloys

“…Thus, easy-axes of neighbouring variants are perpendicular. The corresponding magnetic microstructure is basically determined by the magnetostatic coupling between domains in adjacent twins which present different orientation of their corresponding easy-axes (Armstrong et al, 2008). In each variant, magnetic domains are formed in such a way that the magnetization alternates between two opposite values along the corresponding easy axis.…”

Regulating self-organizing nanostructures via external mechanism

“…1 They have been observed in a wide range of material systems, including polymer blends and block copolymers, 2-4 semiconducting quantum dots and lines, [5][6][7] magnetic domains and nanoparticles, [8][9][10] and martensitic twins and ferroelectric domains. [11][12][13] The phenomena are driven by competing atomic and molecular interactions to minimize the overall energy of the system, with the formation of nanostructure governed by the internal instability, and size of the nanostructure determined by the competition between the refining and coarsening mechanisms.…”