Time dependence of interlayer coupling in Pd(50 Å)/Co(tCo Å)/Pd(54 Å)/Co(tCo Å)/Pd(50 Å) multilayer with perpendicular anisotropy

Time-dependent ferromagnetic (FM)-antiferromagnetic (AFM) interlayer coupling transition has been found in Pd(50 Å)/Co(tCo Å)/Pd(54 Å)/Co(tCo Å)/Pd(50 Å) multilayer. During exposure to the air, saturation magnetic moment and coercivity both drop with time; moreover, a shift of the minor loop center for AFM coupling also decreases with time. During exposure of the sample to the air, as one possibility, the observed time-dependent FM-AFM interlayer coupling transition and decrease of AFM coupling strength may result from absorption of gaseous elements, which can induce reduction of Pd-polarization and a decrease of saturation magnetic moment; another possibility may be the alloying of the Co/Pd interface.