Thermal dependence of coercivity in Co-based nanostructures

The magnetic properties of two morphologically different Go-based systems h ave been studied at low temperature. The systems are a series of Co/Ni mult ilayers grown by sputtering, and CoB ribbons made by the melt-spinning tech nique and thermally treated in order to produce Co nanograins embedded in a ferromagnetic Co-B amorphous matrix. The thermal dependence of the coerciv e force and the AC susceptibility of both samples show a similar qualitativ e behavior, the main feature being the observation of a strong hardening be low 200 K. The experimental results are analyzed on the basis of the degree of magnetic coupling between the hard and the soft phase and of the magnet ic state of the interfacial region. (C) 2000 Elsevier Science B.V. All righ ts reserved.