Altering magnetostrictive strain pathways via morphology of spontaneously aligned domains

In contrast to the use of a mazelike (randomly oriented) magnetic domain morphology or the application of a prestress, it is shown that spontaneously aligned domain morphology is capable of reducing the switching fields and producing a variety of magnetostriction strain pathways that are otherwise not possible by conventional materials approaches (composition and microstructure) alone. Using phase field micromagnetic microelastic modeling, the underlying magnetic domain evolution and the resultant strain behavior of giant magnetostriction materials with uniaxial magnetic anisotropy is explained by analyzing elastostatic interactions across domain walls arising from magnetostriction-induced strain mismatch.

Figure 1

(a) Mazelike or random domain pattern and (b) aligned domain morphology in amorphous Tb${}_{40}$Fe${}_{60}$ films with perpendicular magnetic anisotropy; (a′) and (b′) are the respective schematics.

Figure 2

(a) Schematic of magnetization in two adjacent domains at zero field. (b) and (c) Magnetostrictive distortion of domains due to magnetization rotation with applied field normal and parallel to the domain wall, respectively.

Figure 3

(a) Domain structure and orientation of applied field for three different cases: Cases I and II refer to aligned domains, and magnetic field normal (${\mathbf{H}}_{\perp }$) and parallel (${\mathbf{H}}_{\parallel }$) to domain walls, respectively; case III refers to random domains under magnetic field (H). (b) Simulated magnetization and (c) strain curves for cases I and II. (d) Simulated magnetization (left-hand axis) and strain curve (right-hand axis) for case III. (e) Magnetization curves for the three cases with zero magnetostriction as a comparison. (f) Misfit strain energy during the magnetization process for the three cases.