Magnetoresistance of Fe-Ni invar alloy and Cu trilayer

In this paper, we report the field and temperature dependence of magnetoresistance of trilayer made by sandwitching Cu layer between two Fe-Ni layers. Two trilayer structures have been prepared (i) Fe0.59Ni0.41 (50 nm)/Cu (8 nm)/ Fe0.59Ni0.41 (50 nm) (non invar trilayer) and (ii) Fe0.61Ni0.39 (50 nm)/Cu (8 nm)/ Fe0.61Ni0.39 (50 nm) (invar trilayer). The magnetoresistance of invar trilayer exhibits anomalous temperature and field dependence. The magnetoresistance changes from positive to negative when the temperature changes from 5K to 100K. Whereas the magnetoresistance of the non invar trilayer resembles the usual ferromagnetic trilayer and remains positive down to low temperatures. The anomalous magnetoresistance in invar trilayer is related to the existence of two magnetic states.