Nanoscale magnetization inhomogeneity within single phase nanopillars

Self-assembling three-dimensional nanostructures are the ideal platforms to achieve strain mediated heterogenous multiferroics, as the strained interfacial area scales with film thickness. The archetypal example, epitaxially strained CoFe${}_{2}$O${}_{4}$ nanopillars embedded in a BaTiO${}_{3}$ matrix, possesses significant out-of-plane uniaxial magnetic anisotropy. In this paper, the authors identify two regions in the CoFe${}_{2}$O${}_{4}$ nanopillars with different magnetic anisotropies. Using micromagnetic simulations and polarized small-angle neutron scattering, they elucidate the consequence of varying anisotropy within the pillar on its magnetization reversal. As the length scales of inhomogeneities of the magnetic anisotropy and the displacement field from the CoFe${}_{2}$O${}_{4}$-BaTiO${}_{3}$ interface are similar, strain-mediated ferroic materials using vertically aligned nanopillars may provide new functionality for potential applications in low-power memory, computing, and sensing.