Effect of annealing temperature on exchange coupling in NiFe∕FeMn and FeMn∕NiFe systems

Most studies on exchange bias in spin valves are for antiferromagnetic/ferromagnetic structures, and Fe[50]Mn[50]∕Ni[79]Fe[21] is widely used. The results of the exchange-bias field (Hex) and coercivity (Hc) as a function of the annealing temperature in NiFe∕FeMn and FeMn∕NiFe systems are given in the study. We prepare two types of films, type I: substrate/∕Ta∕NiFe∕FeMn∕Ta and type II: substrate/Ta∕FeMn∕NiFe∕Ta, respectively. Annealing was performed at 150–450°C under 720Oe for 2h, Hex and Hc of type I samples increase slightly with the increase of the annealing temperature. But Hex and Hc of type II samples increase rapidly after annealing over 300°C, then decrease after annealing at 375°C. The strong exchange-bias field and low coercivity were exhibited for type I samples, where NiFe is the buffer layer and is also the pinned layer. In type II samples, the increase in the exchange-bias field is attributed to the altered interface of FeMn∕NiFe due to interdiffusion. The interpretation of the fluctuation ...