ULTRAHIGH-VACUUM SQUID MAGNETOMETRY STUDY OF THE MAGNETIC-PROPERTIES OF CO CO-OXIDE THIN-FILMS/

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 faci lity were transported into the UHVSQM without breaking vacuum and magn etically characterized before and after in situ room temperature oxida tion. Field-cooled hysteresis measurements performed at low temperatur es indicate the presence of a complex antiferromagnetic Co-oxide domai n structure as a result of oxidation. The stability of the magnetic st ructure is determined by competition between frustration generated at the interface when the ferromagnetic Co moments are reversed and stabi lizing antiferromagnetic anisotropy which becomes large only at low te mperatures (<150 K). (C) 1996 American Institute of Physics.