Strain Engineering of Magnetic Anisotropy in Epitaxial Films of Cobalt Ferrite

Abstract

Perpendicular magnetic anisotropy (PMA) energy up to $K_{\mathrm{u}}=6.1\pm 0.8$ MJ m${}^{-3}$ is demonstrated in this study by inducing large lattice-distortion exceeding 3% at room temperature in epitaxially distorted cobalt ferrite Co${}_x$Fe${}_{3-x}$O${}_4$ (x = 0.72) (001) thin films. Although the thin film materials include no rare-earth elements or noble metals, the observed $K_u$ is larger than that of the neodymium-iron-boron compounds for high-performance permanent magnets. The large PMA is attributed to the significantly enhanced magneto-elastic effects, which are pronounced in distorted films with epitaxial lattice structures upon introducing a distortion control layer of composition Mg${}_{2-x}$Sn${}_{1+x}$O${}_4$. Surprisingly, the induced $K_u$ can be quantitatively explained in terms of the agreement between the local crystal field of Co${}^{2+}$ and the phenomenological magneto-elastic model, indicating that the linear response of induced $K_u$ is sufficiently valid even under lattice distortions as large as 3.2%. Controlling tetragonal lattice deformation using a non-magnetic spinel layer for ferrites could be a promising protocol for developing materials with large magnetic anisotropies.

22 pages, 11 figures

References in corpus (1)

• Magnetization and Anisotropy of Cobalt Ferrite Thin Films