Strain-Controlled Giant Magnetoresistance in Spin Valves Grown on Shape Memory Alloys

We report a strain-mediated giant magnetoresistance (GMR) in spin valves (SPVs) grown on shape memory alloys (SMAs). The SPVs with a stacking structure of Al2O3/Co90Fe10/Cu/Co90Fe10/IrMn/Pt were deposited on NiTi and NiTiNb SMA substrates with and without predeformation. The GMR of the SPVs on the precompressed NiTi substrates changes after annealing, whereas the one on SMAs without predeformation remains unchanged under the same annealing treatment. Especially, the GMR of the SPVs on the NiTiNb substrates can be reversibly modulated under a thermocycling treatment on account of the shape memory effect caused by the phase transitions of NiTiNb. The study demonstrates a new strain-mediated approach to reversibly control GMR through phase transitions, which provides a potential way to design strain-sensitive spintronic devices.