Ultrahigh vacuum SQUID magnetometry study of the magnetic properties of Co/Co-oxide thin films

Abstract

Exchange coupling between Co and Co-oxide in bilayer and trilayer thin-film structures has been studied using a recently developed ultrahigh vacuum SQUID magnetometer (UHVSQM) system. Using this novel technique, newly deposited Co films from a separate molecular beam epitaxy facility were transported into the UHVSQM without breaking vacuum and magnetically characterized before and after in situ room temperature oxidation. Field-cooled hysteresis measurements performed at low temperatures indicate the presence of a complex antiferromagnetic Co-oxide domain structure as a result of oxidation. The stability of the magnetic structure is determined by competition between frustration generated at the interface when the ferromagnetic Co moments are reversed and stabilizing antiferromagnetic anisotropy which becomes large only at low temperatures (<150 K).