Iron exchange-field penetration into the amorphous interphase of nanocrystalline materials

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Abstract
In this work an enhancement of the Curie temperature of the intergranular amorphous region in nanocrystalline alloys with respect to amorphous ribbons of the same composition is shown. The Curie temperature reaches a value of 125 °C. The experimental results are discussed in terms of both an inhomogeneous distribution of Nb atoms in the interphase and the magnetic interactions between the Fe ferromagnetic grains and the matrix. Finally, it is proposed that the existence of a molecular field of about 80 T originated by the penetration of the exchange field of α-Fe nanocrystals into the amorphous paramagnetic intergranular region is the main cause of this Curie temperature enhancement. Moreover, the compositional dependence of the Curie temperature in Fe-B-Nb-Cu amorphous ribbons has been reported.