Magnetic anisotropy of [Co2MnSi/Pd]n superlattice films prepared on MgO(001), (110), and (111) substrates

Superlattice films with full-Heusler Co2MnSi (CMS) alloy and Pd layers prepared on Pd-buffered MgO(001), (110), and (111) substrates were investigated. Crystal orientation and epitaxial relationship of Pd and CMS layers were analyzed from x-ray diffraction, pole figure measurements, and transmission electron microscope observation. Formation of the L21-ordered structure in the CMS layers was confirmed by observation of CMS(111) diffraction. Perpendicular magnetic anisotropy (PMA) was obtained in the [CMS (0.6 nm)/Pd (2 nm)]6 superlattice film formed using MgO(111) substrates although other superlattice films prepared using MgO(001) and (110) substrates showed in-plane and isotropic magnetic anisotropy, respectively. The perpendicular magnetic anisotropy energy constant K for the superlattice films prepared using MgO(111) substrate was estimated to be 2.3 Mergs/cm3, and an interfacial anisotropy constant Ki per one CMS-Pd interface in the superlattice films was estimated to be 0.16 ergs/cm2. Ki in superlattice films with various crystal orientations showed positive values, indicating that Pd/CMS interfaces had an ability to induce PMA regardless of their crystal orientation.