Temperature dependence of exchange field in exchange-spring magnets

Pr8Fe88B4 ribbons prepared by melt spinning have been investigated by x-ray diffraction, differential thermal analysis, thermomagnetic analysis, atom force microscopy, and superconducting quantum interface device magnetometer . The results show that the annealed ribbons consist of the Pr2Fe14B and al pha -Fe phases. The magnetization of soft alpha -Fe phase remains parallel to the magnetization of the hard Pr2Fe14B phase for fields less than the ex change field (H-ex). The exchange field in exchange-spring magnets, determi ned from the demagnetization curves measured at various temperatures, incre ases with decreasing grain size and measure temperature. The temperature de pendence of exchange field was analyzed qualitatively by the expression H-e x = (AK)(1/2)/(M(s)t). (C) 2001 American Institute of Physics.