Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film

TLDR

Perpendicular magnetization and precise control over the magnetic easy axis in thin films are essential for applications such as magnetic recording media. The present approach enables systematic tuning of the magnetic easy axis and coercivity in the desired direction by manipulating crystal orientation at the nanoscale. Post‑annealing of an oxygen‑deficient porous CoFe₂O₄ film induces compressive strain perpendicular to the surface, producing large perpendicular coercivity. The study shows that a strong (111) orientation can be achieved at 100 °C, yielding a 40‑nm CoFe₂O₄ film with an unprecedented 11.3 kOe perpendicular coercivity, and that this high coercivity is attainable on virtually any substrate.

Abstract

Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate.