Exchange bias, training effect, hysteretic behavior of angular dependence, and rotational hysteresis loss in NiFe/FeMn bilayer: Effect of antiferromagnet layer thickness

For NiFe/FeMn bilayers, the correlation among the exchange field, the coercivity, the training effect, the hysteretic effect of the angular dependence of the exchange bias, and the rotational hysteresis loss has been studied as a function of the antiferromagnet layer thickness tAFM. With increasing tAFM, all these quantities undergo nonmonotonic variations, except for the monotonic change in the exchange field. The maximal values of the coercivity, its relative change, and the rotational hysteresis loss are almost located at the same tAFM of 3.8 nm. The maximal values of the relative change in the exchange field and of the hysteretic effect of the angular dependence are located at 2.5 and 3.0 nm, respectively. The rotational hysteresis loss and the hysteretic behavior of the angular dependence of the exchange bias have different characteristics. The variations of all physical quantities with tAFM can be ascribed to the irreversible reversal of the antiferromagnet spins, which are governed by the Arrhenius...