Thermal Magnetic Behavior of Nanocrystalline Fe73.5Cu1Nb3Si13.5B9 Ribbons

Thermal magnetic behavior and microstructure of Fe73.5Cu1Nb3Si13.5B9 ribbon annealed at different temperatures were investigated. It was indicated that the onset crystallization temperature of the ribbon was around at 530 degrees C and its Curie temperature can be enhanced from 320 degrees C to 385 degrees C by annealing. X-ray diffraction structural analysis showed that a single a-FeSi crystalline phase with grain size about 12 nm was precipitated from amorphous matrix for FeCuNbSiB ribbons annealed between 530 degrees C and 580 degrees C. The alpha-FeSi phases were octahedral shape confirmed by the morphology simulation and the AFM method. The thermal magnetic behaviors were complicated, as the mu(i) can be divided into two modes during increasing temperature, but for the Bs and Ms shown a normal decrease with increasing temperature. The coercive force Hc and remanence ratio alpha have shown a continuous monotonic decline in single-phase ribbon with increasing temperature, and increased to a max value or a peak and then decreased to zero in biphase ribbons. The thermal behaviors of magnetic properties were controlled by the exchange coupling interaction between the alpha-FeSi grains and the intergranular amorphous phase. It is important to maintain an efficient exchange coupling interaction between alpha-FeSi grains and the residual amorphous matrix, and it is necessary to sustain the higher Curie temperature for the application of the FeCuNbSiB ribbons in high temperature by controlling the size and crystallization degree of alpha-FeSi grains.