EXCHANGE COUPLING AND ENHANCEMENT OF CURIE TEMPERATURE OF THE INTERGRANULAR AMORPHOUS REGION IN NANO-CRYSTALLINE DUPLEX-PHASE ALLOYS SYSTEM

Abstract

We studied the theoretical Curie temperature of a dual-phase nanomagnetic system by Monte Carlo simulation of a modified Heisenberg model on a 3D complex lattice consisting of single- and cluster-spins. We also systematically investigated the experimental Curie temperature of a dual-phase nanomagnetic alloy and performed a direct comparison between theory and experiment. The exchange coupling between two component magnetic phases substantially affects the Curie temperature [Formula: see text] of the intergranular amorphous region of a dual-phase nanomagnetic system. The [Formula: see text] depends upon the nanocrystallite size d, the volume fraction Vc and the interspace among crystallites ξ. Large crystallized volume fraction Vc, small grain size d, and thin interphase thickness ξ lead to an obvious enhancement of Curie temperature (ECT) of intergranular amorphous region, whereas the Curie temperature of nanocrystallites [Formula: see text] decreases slightly. By simulation, we worked out a relationship between the reduced ECT and ξ, as [Formula: see text], and it conforms to the experimental result. In addition, we also simulated the demagnetization of a hard–soft nanocomposite system. The exchange coupling between two component phases affects the cooperativity of two-phase magnetizations, the coherent reversal of magnetizations, and coercivity.