Magnetic properties, phase evolution and microstructures of Pr9.44Fe90.56?xBx (x=7.16 and 4.76) nanocomposite magnets have been investigated. Both as-spun ribbons exhibit two-step demagnetization curves, indicating the feature of partial crystallization. By using di?erential scanning calorimeter (DSC) measurements, remained amorphous phase of ribbon with x=7.16 shows a higher crystallization temperature. At optimum annealing temperature of 650 ?C for 10 min, better magnetic properties, Mr=1.01 T, jHc=796 kA/m and (BH)max=136 kJ/m3 were obtained in the sample with x=4.76. Transmission electron microscopy (TEM) observation confirms that the sample with x=4.76 possesses much finer grain size, which causing a better exchange coupling between soft and hard magnetic grains.
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