Engineering irreversibility of exchange springs in antiferromagnetic DyFe2/YFe2 superlattices

Abstract

Irreversible exchange springs are experimentally observed in an antiferromagnetic (DyFe2 40 Å/YFe2 80 Å/DyFe2 8 Å/YFe2 80 Å) × 20 superlattice. Two irreversible exchange springs can be observed at 80 K with field along the [00] crystal direction. OOMMF micromagnetic simulation is employed to understand the underlying physics. It is confirmed that the induced anisotropy in the soft phase, by the 8 Å thick DyFe2 layer, is mainly responsible for the observed irreversibility, which corresponds to switching between energy minima of the thin hard inclusion in the soft phase. The qualitative agreement between experiment and simulation is satisfactory. This demonstrates the feasibility to control the irreversibility of exchange spring winding and unwinding processes in antiferromagnetically coupled superlattices. This additional degree of freedom in the demagnetization process of the soft layers of exchange coupled superlattices can be utilized to reduce the switching field of a hybrid magnet through spin-wave assisted magnetization reversal.