Control of Magnetic Shape Anisotropy by Nanopillar Dimensionality in Vertically Aligned Nanocomposites

Perpendicular magnetic anisotropy forms the foundation of the current data storage technology. However, there is an ever-increasing demand for higher density data storage, faster read-write access times, and lower power consuming storage devices, which requires new materials to reduce the switching current, improve bit-to-bit distributions, and improve reliability of writing with scalability below 10 nm. Here, vertically aligned nanocomposites (VANs) composed of self-assembled ferromagnetic La_0.7Sr_0.3MnO₃ (LSMO) nanopillars in a surrounding ZnO matrix are investigated for controllable magnetic anisotropy. Confinement of LSMO into nanopillar dimensions down to 15 nm in such VAN films aligns the magnetic easy axis along the out-of-plane (i.e., perpendicular) direction, in strong contrast to the typical in-plane easy axis for strained, phase pure LSMO thin films. The dominant contribution to the magnetic anisotropy in these (LSMO)_0.1(ZnO)_0.9 VAN films comes from the shape of the nanopillars, while the epitaxial strain at the vertical LSMO:ZnO interfaces exhibits a negligible effect. These VAN films with their large, out-of-plane remnant magnetization of 2.6 μB/Mn and bit density of 0.77 Tbits/inch² offer an interesting strategy for enhanced data storage applications.