Doubly exchange-biased NiCoO/NiFe/Cu/NiFe/NiCoO spin valves

Abstract

A new type of doubly exchange-biased Ni50Co50O/NiFe/Cu/NiFe/Ni30Co70O spin-valve structure, with two ferromagnetic layers exchange biased in opposite directions by two different antiferromagnetic layers is demonstrated. By field cooling in magnetic fields of opposite directions, the resultant hysteresis loop consists of two loops shifted in opposite directions from the zero magnetic field. The NiFe layers are in the antiparallel state in zero magnetic field, and the switching to the parallel state can be tuned by varying the exchange bias. The modified spin valves also show potential for suppressed Barkhausen noise.