Effect of flash thermal annealing by pulsed current on rotational anisotropy in exchange-biased NiFe/FeMn film

Abstract

In this paper, Ta/[NiFe(15 nm)/FeMn(10 nm)]/Ta exchange-biased bilayers are fabricated by magnetron sputtering, and their static and dynamic magnetic properties before and after rapid annealing treatment with pulsed current are characterized by using a vibrating sample magnetometer (VSM) and a vector network analyzer (VNA), respectively. The exchange bias field H e and static anisotropy field H sta k decrease from 118.45 Oe (1 Oe = 79.5775 A•m −1 ) and 126.84 Oe at 0 V to 94.75 Oe and 102.31 Oe at 90 V, respectively, with increasing capacitor voltage, which supplies pulsed current to heat the sample. The effect of flash thermal annealing by pulsed current on the rotational anisotropy (H rot ), the difference value between static and dynamic magnetic anisotropy, is investigated particularly. The highest H rot is obtained in the sample annealing with 45-V capacitor (3300 µF) voltage. According to the anisotropic magnetoresistance measurements, it can be explained by the fact that the temperature of the sample is around the blocking temperature of the exchange bias system (T b ) at 45 V, the critical temperature where the formation of more unstable antiferromagnetic grains occurs.