Activation energy of interdiffusion and interface structure for CoFe/Cu spin-valves

Annealing time and temperature dependences of MR ratio in CoFe/Cu spin-valves were investigated. Thermal deterioration of MR ratio was well explained by considering two phenomena with effective activation energies of 2.16 eV and 1.57 eV for CoZrNb/NiFelCoFe/Cu/CoFe/FeMn spin-valves, and considering one phenomenon with a value of 2.49 eV for CoZrNb/NiFe/CoFe/Cu/CoFe/IrMn spin-valves, respectively. These values are in good agreement with activation energies of interdiffusion based on the vacancy mechanism. It is shown that no significant change in MR ratio is evaluated from the effective activation energies for the period of more than 10 years at 150/spl deg/C in CoZrNb/NiFe/CoFe/Cu/CoFe/IrMn spin-valve films.