Exchange-spring Nd-Fe-B alloys: Investigations into reversal mechanisms and their temperature dependence

摘要

In order to investigate factors affecting coercivity a series of two-phase Nd(sub 2)Fe(sub 14)B-based nanocomposite alloys with different excess iron concentrations were produced by melt-spinning methods. The constituent grain size was estimated by diffraction methods to be in the range of 150 (Angstrom) - 500 (Angstrom), and room-temperature demagnetization curves verify that the alloys studied exhibit a modest remanence enhancement. Isothermal remanence magnetization (IRM) and dc-demagnetization (DCD) measurements performed at temperatures in the range 275 K (le) T (le) 350 K illustrate that the coercivity and irreversible magnetization develops in a bimodal, incoherent manner from a demagnetized state but upon demagnetization from a saturated state the system evinces collective, exchange-coupled behavior as illustrated by the reversible magnetization M(sub rev). The temperature dependencies and values of the irreversible susceptibility X(sub irr) (DCD) suggest that a moderating phase with a magnetic anisotropy intermediate to the two constituent main phases may be present in the alloys.