EXCHANGE-SPRING ND-FE-B ALLOYS - INVESTIGATIONS INTO REVERSAL MECHANISMS AND THEIR TEMPERATURE-DEPENDENCE

In order to investigate factors affecting coercivity a series of two-p hase Nd2Fe14B-based nanocomposite alloys with different excess iron co ncentrations were produced by melt-spinning methods. The constituent g rain size was estimated by diffraction methods to be in the range of 1 50-500 Angstrom, and room-temperature demagnetization curves verify th at the alloys studied exhibit a modest remanence enhancement. Isotherm al remanence magnetization (IRM) and de demagnetization (DCD) measurem ents performed at temperatures in the range 275 K less than or equal t o T less than or equal to 350 K illustrate that the coercivity and irr eversible magnetization develop in a bimodal, incoherent manner from a demagnetized state but upon demagnetization from a saturated state th e system evinces collective, exchange-coupled behavior as illustrated by the reversible magnetization M-rev. The temperature dependencies an d values of the irreversible susceptibility X-irr (DCD) suggest that a moderating phase with a magnetic anisotropy intermediate to the two c onstituent main phases may be present in the alloys. (C) 1997 American Institute of Physics.