Perpendicular magnetic anisotropy in ferrimagnetic Mn4N films grown on (LaAlO3)0.3(Sr2TaAlO6)0.7(0 0 1) substrates by molecular beam epitaxy

Abstract

Many studies have shown that Mn4N thin films possess perpendicular magnetic anisotropy (PMA) caused by in-plane tensile strain. Since cubic (LaAlO3)0.3(Sr2TaAlO6)0.7 [LSAT] (0 0 1) has a smaller lattice constant than Mn4N with a mismatch of 0.8%, a compressive strain is expected to be induced in Mn4N epitaxial films grown on an LSAT substrate. We grew Mn4N thin films on an LSAT(0 0 1) substrate by molecular beam epitaxy, and investigated the optimum growth temperature (TS) from the aspects of crystallinity, magnetic properties, and magneto-transport properties. Mn4N films were grown epitaxially at temperatures between TS = 700 and 800 °C with maintaining PMA, and the optimum TS was determined to be approximately 750 °C. In-plane and out-of-plane X-ray diffraction measurements showed that the Mn4N films were under tensile stress in contrast to our prediction. From the thickness dependence of magnetization, a dead layer of approximately 10 nm existed at the Mn4N/LSAT interface. Transmission electron microscopy observation revealed that Mn-N composites other than Mn4N existed in the early stage of MBE growth.