Metastable L11 and B h Ordered Phase Formation in CoPt Alloy Thin Films Epitaxially Grown on Metal Underlayers

Abstract

Co50Pt50 (at. %) alloy epitaxial thin films with the close-packed plane parallel to the substrate surface are prepared on fcc-Pt, fcc-Pd, fcc-Cu, bcc-Cr, hcp-Ti, and hcp-Ru underlayers hetero-epitaxially grown on MgO(111) single-crystal substrates at 300 {degree sign}C by using a radio-frequency magnetron sputtering system. Ordered phase formation is recognized for CoPt films grown on all the underlayers. The ordered phase is determined from a view-point of stacking sequence of close-packed plane. The CoPt films formed on fcc underlayers consist of L11 ordered phase, whereas those grown on bcc and hcp underlayers involve B h ordered phase in addition to L11 ordered phase. These ordered films show strong perpendicular magnetic anisotropies reflecting the magnetocrystalline anisotropies of L11- and/or B h-CoPt crystals.