Temperature dependence of biased hysteresis loops in hard-soft nanocrystalline Co-based ribbons

The low field hysteresis loops of hard-soft magnetic materials can be biased as a consequence of the magnetic coupling of both phases. In hard-soft nanocrystalline materials, magnetostatic and exchange interactions between the hard crystalline phase and the much softer embedding amorphous matrix coexist and the relevance of their effect on the hysteresis is difficult to distinguish. In this work, the thermal evolution of the biased magnetic hysteresis loops of hardsoft devitrified Co66Fe4Mo2Si16B12 ribbons has been studied between room and Curie temperature. The nature of the coupling between the two magnetic phases is discussed in terms of the influence of the temperature on the magnetic properties of the soft phase, mainly on its saturation magnetization and exchange constant, and on the switching field distribution of the hard phase. The results allow to conclude that the effect of the exchange interaction predominates over the magnetostatic one.