Thermal stability of exchange coupling in permalloy/FeMn bilayers and its dependence on the antiferromagnetic layer thickness

摘要

For permalloy/FeMn bilayers, the exchange field and coercivity exponentially decay in time with the application of an applied field antiparallel to the unidirectional anisotropy direction. The relative change of the exchange field, 1-H_(E)(t=∞)/H_(E)(t=0), also decays in an exponential manner with the FeMn layer thickness. This dependence can be explained by using a thermal fluctuation theory. Moreover, calculations show that the thermal stability of the exchange coupling is independent of the permalloy layer thickness. These findings may be helpful to the design of the spin-valve giant magnetoresistance devices.