Tunable magnetic exchange springs in semiconductor GdN/NdN superlattices

We report twisted magnetization phases, i.e., exchange springs, across interfaces in a semiconducting NdN/GdN superlattice and compare the exchange springs to those reported previously across SmN/GdN interfaces. Like SmN, NdN has an orbital moment larger than and opposing its spin magnetic moment, resulting in exchange-Zeeman competition that in turn precipitates the exchange springs. In contrast to SmN, NdN has a large net magnetic moment, adding more complexity to the exchange-spring behavior. We investigate how different temperatures and applied magnetic fields influence the twisted magnetization using complementary magnetometry and element specific x-ray magnetic circular dichroism. The exchange spring can be driven into two different phases, with either the hard NdN or soft GdN entering the twisted phase. This tunable twisted magnetization in ferromagnetic semiconductors could open up a pathway to control tunneling magnetoresistance in spintronics devices, encouraging further investigation of these new types of exchange springs.