Curie-temperature enhancement of ferromagnetic phases in nanoscale heterogeneous systems

The dependence of Ni Curie temperature, T-C, on the Ni thickness in Co-Ni and Ag-Ni multilayers is reported. It is shown that T-C increases 60 degrees C for the Co-Ni samples, as the Ni thickness decreases from 100 to 50 Angstrom. The difference in T-C between Co-Ni and Ag-Ni multilayers increases as the Ni thickness decreases, reaching 75 degrees C for 25 Angstrom thickness. We propose as a possible explanation that the molecular field of Co layers penetrates into the Ni layer so enhancing T-C. The influence on the coercive field of the Ni transition from ferromagnetic to paramagnetic state is also shown.