Abstract

An exchange spring magnet is a magnetic material with high coercivity and high saturation properties derived from the exchange interaction between a hard magnetic material and a soft magnetic material, respectively. In recent years, it has been shown that multilayers, consisting of alternating hard RFe2 layers (R = Dy or Er) and soft YFe2 layers, are excellent model systems for the study of magnetic exchange springs. We had a closer look at these systems with a help of x-ray magnetic circular dichroism and micro-magnetic simulations.

Using a history-dependent procedure, which involves both rotation and magnetization routines the supperlattice can be driven to a transverse magnetic exchange spring state. The key features of the transverse state are near zero signals in remanence and reversibility in small applied fields. However, in larger fields in-plane transverse exchange spring state is lost, being replaced by an irreversible out-of-plane magnetic exchange spring loop.

The insertion of few layers of DyFe2 or ErFe2 into the soft YFe2 layer makes the system even more complex resulting in variety of distinct spring states.