Magneto-optical properties of Co/Ge (100) with ultrathin Ag buffer layers

Magnetic properties of Co films (<2 nm) with Ag buffer layers (<0.7 nm) grown on Ge(100) at room temperature and 200 K were studied by surface magneto-optical Kerr effect. Without the buffer, the films reveal in-plane magnetic anisotropy even Co and Ge forms nonmagnetic interfacial alloys. The hysteresis due to intercalation of Ag can be detected at thinner Co thicknesses. The buffer can effectively cutoff the intermixing of Co and Ge. As the thickness of Ag is reduced, out-of-plane magnetic anisotropy due to the interface interactions between CoAg and CoGe was discovered and was only at 200 K.