HETEROEPITAXIAL GROWTH OF PT CO MULTILAYERS ON SINGLE-CRYSTAL ZNO/

We have epitaxially grown Pt/Co multilayers by sputtering and vapor-de position directly on single crystals of ZnO, so that Pt/Co (111)parall el to ZnO (0001) and Pt/Co [1 ($) over bar 10]parallel to[1 ($) over b ar 10] ZnO, as characterized by high resolution electron microscopy in sputtered films, and by low energy electron diffraction in evaporated films. These multilayers had very large perpendicular magnetic anisot ropy energy, K-eff = 2.4 x 10(7) erg/cm(3)-Co (2.4 MJ/m(3)-Co) and 3.2 x 10(7) erg/cm(3)-Co (3.2 MJ/m(3)-Co), respectively for sputtering an d vapor deposition. Whereas the coercivity was only modest for the spu ttered multilayers, H-c = 1.1 kOe (87 kA/m), it was relatively large f or vapor-deposition, H-c = 3.6 kOe (290 kA/m). We attributed these lar ge anisotropy energies to (Ill)fcc, multilayer epitaxy on (0001) ZnO, and differences in coercivity to individual growth-induced microstruct ural features, which we characterized by electron probe microscopies. Epitaxy did not occur on a ZnO(1 ($) over bar 100) surface, and Pt/Co multilayers vapor-deposited on this surface had inferior (111) texture and a much smaller anisotropy energy, similar to 1 MJ/m(3)-Co.