Exchange bias coupling of Co with ultrathin La2/3Sr1/3MnO3 films

Magnetic properties of epitaxially grown ultrathin La2/3Sr1/3MnO3 (LSMO) films down to a thickness of one unit cell (u.c.) have been systematically investigated by studying their magnetic behaviors with Co capping layers. For LSMO thickness below 3 u.c., the Co/LSMO bilayers exhibit strong exchange bias (EB) effects after field cooling, suggesting the existence of antiferromagnetic (AFM) phase at the interfaces in ultrathin LSMO. The presence of exchange bias effect for the bilayer with 1 u.c. thick LSMO further demonstrates that the AFM ordering of the LSMO is C-type AFM ordering structure. For 10 u.c. LSMO, the magnetic properties are clearly not altered by the capping Co film, suggesting that the observed phenomena are caused by the intrinsic properties of LSMO.