Influence of gas adsorption at the interface on the exchange coupling field of Ni-Fe/25at%Ni-Mn/Ni-Fe films

The influence of gas adsorption at the interface on the exchange coupling field was investigated for Ni-Fe 200 /spl Aring//25at%Ni-Mn 200 /spl Aring//Ni-Fe 300 /spl Aring/ trilayer films deposited on Si(100) substrate. When the interface between the lower Ni-Fe layer and the Ni-Mn layer was exposed to an atmosphere with leaking air, 5/spl times/10/sup -8//spl sim/2/spl times/10/sup -6/ Torr for 60 min, unidirectional anisotropy constant, J/sub k/ at the both interfaces abruptly decreased at 1/spl times/10/sup -7/ Torr of exposed pressure and vanished at 2/spl times/10/sup -7/ Torr. The vanishing J/sub k/ was strongly correlated with disappearance of /spl gamma/-Ni-Mn phase verified by TEM observation. In order to clarify the gas species which adsorb on the Ni-Fe surface and suppress the formation of /spl gamma/-Ni-Mn phase on it, the exposure of the interface under various pure gas atmosphere (N/sub 2/, O/sub 2/, H/sub 2/O) was examined. As a result, oxygen was confirmed to be the most probable gas element, and the surface oxidation of Ni-Fe layer was found to prevent the epitaxial growth of /spl gamma/-Ni-Mn grains on it.