Curie-temperature enhancement of ferromagnetic phases in nanoscale heterogeneous systems

The dependence of Ni Curie temperature, TC, on the Ni thickness in Co-Ni and Ag-Ni multilayers is reported. It is shown that TC increases 60 ^∘{}C for the Co-Ni samples, as the Ni thickness decreases from 100 to 50 {}. The difference in TC between Co-Ni and Ag-Ni multilayers increases as the Ni thickness decreases, reaching 75 ^∘{}C for 25 {} thickness. We propose as a possible explanation that the molecular field of Co layers penetrates into the Ni layer so enhancing TC. The influence on the coercive field of the Ni transition from ferromagnetic to paramagnetic state is also shown. {} 1996 The American Physical Society.