Magnetic oxide nanowires with strain-controlled uniaxial magnetic anisotropy direction

Abstract

While magnetic nanowires generally have a preferential magnetization direction along the wire axis to minimize magnetostatic energy, it is shown here for epitaxial magnetic oxide nanowires that substrate-induced strain can be used to tailor the magnetic easy axis in any direction. ${\text{La}}_{0.67}{\text{Sr}}_{0.33}{\text{MnO}}_{3}$ (LSMO) nanowires were prepared by pulsed laser deposition of LSMO thin films on ${\text{NdGaO}}_{3}$ (NGO) substrates of two different orientations [$\text{NGO}{(110)}_{\text{o}}$ and $\text{NGO}{(010)}_{\text{o}}$], followed by patterning into arrays of nanowires by laser interference lithography. The uniaxial compressive strain from the substrate induces a strong uniaxial magnetic anisotropy in the LSMO that dominates the anisotropy. Hence, one obtains LSMO nanowires having a magnetic easy axis that can lie in any direction, including perpendicular to the wire axis. In marked contrast, similar nanowires on ${\text{SrTiO}}_{3}(001)$ substrates without significant uniaxial strain exhibit the usual preferential magnetization direction along the wire axis, as dictated by magnetostatic shape anisotropy. The tunable magnetic anisotropy direction is a useful feature for applications of magnetic nanowires in magnetic memory, sensor, and logic devices.