In situ magnetoresistance measurements during patterning of spin valve devices

An in situ magnetoresistance test rig has been designed and built into an argon ion milling rig. The results of these experiments allow direct analysis of the evolution of magnetic and electrical properties of ferromagnetic structures. Arrays of wires of equal mark/space ratio were patterned using photolithography in the 15 nm thick top layer of Ni80Fe20trilayers with the structure: Ta(3nm)/Ni80Fe20(6nm)/Cu(2. 2nm)/Ni80Fe20(15nm)/Ta(3nm). The in situ test rig was used to analyze the change in the magnetoresistance response as the anisotropy of the top layer was increased during milling. The results show that it is possible to partially decouple the Ni80Fe20ferromagnetic layers with large milling depths and a small spin valve response is observed. It is also shown that as the anisotropy of the top layer is further increased by decreasing the width of the wires, the spin valve response is magnified. This spin valve design has considerable potential for high temperature device operation.