Effect of degree of die upset on magnetic behavior in Nd-13.9(Fe0.92Co0.08)(80.3)B5.3Ga0.5

DC demagnetization (DCD), isothermal remanent magnetization (IRM), and reve rsible magnetization measurements were used to examine the magnetic reversa l behavior in melt-quenched samples of composition Nd-13.9(Fe0.92Co0.08)(80 .3)B5.3Ga0.5 subjected to different levels of thermomechanical deformation (die upsetting). The reversible magnetization measurements indicate that in the thermally demagnetized condition domain walls are present within the m aterial for all levels of deformation. During demagnetization from a satura ted state, domain walls are present in a minority of grains at low levels o f deformation but these domain walls disappear at higher levels of deformat ion. This behavior is explained in terms of changes in the relative strengt hs of nucleation and pinning fields. Comparison of these results to previou s results obtained on similar materials indicate that changes in the magnet ization behavior with degree of deformation are more marked in samples whic h are free of Ga, indicating that Ga additions act to suppress the nucleati on of new domain walls, presumably in the grain boundaries. (C) 2000 Americ an Institute of Physics. [S0021-8979(00)23808-5].