UNUSUAL MAGNETIC-PROPERTIES IN CU/NI MULTILAYERED FILMS

Cu/Ni multilayered films of different layer thicknesses were made by the sputtering technique. In all samples the Cu and Ni layers had the same thickness, and the total thickness of the sample was 5000 Å. Each sample was cooled in zero field to 5 K and the magnetization versus temperature was measured after a magnetic field was applied and kept constant during the experiment. As in spin-glasses, the magnetization of all samples had a peak and was irreversible. In addition, for the 0.1-kOe field, the temperature at which the peak occurred, Tp, decreased as the thickness of the individual layers decreased. This behavior is similar to that of Cu-Mn films, where the spin-glass transition temperature Tg decreases as the spin-glass film thickness decreases [G. G. Kenning, J. Slaughter, and J. Cowen, Phys. Rev. Lett. 59, 2596 (1987)]. The alloying of Cu and Ni at the interfaces probably plays a significant role in causing the spin-glass-like magnetic properties in the Cu/Ni multilayered system.