Epitaxial L1₀-MnAl Thin Films with High Perpendicular Magnetic Anisotropy and Small Surface Roughness

L1₀-ordered MnAl thin films were epitaxially grown by sputtering technique. The substrate and annealing temperature dependences of the structural and magnetic properties of the films were systematically investigated to improve the magnetic properties and surface roughness. A low substrate temperature and subsequent post-annealing are the useful process to obtain MnAl films with both high magnetic anisotropy K u and small surface roughness R a. We have successfully fabricated MnAl thin films deposited on MgO substrates and Cr₉₀Ru₁₀ buffer layers with the very high K u of 13 Merg/cm³, relatively small magnetization of 500 eμcm³, and small R a of 0.34 nm by optimization of the substrate and post-annealing temperatures. The obtained MnAl films will be greatly useful to realize the high-density spin-transfer-torque magnetic random access memory.