Effective anisotropy, exchange-coupling length and coercivity in Nd8−xRxFe87.5B4.5 (R=Dy, Sm, x=0–0.6) nanocomposite

Nd8−xRxFe87.5B4.5 (R=Dy, Sm, x=0–0.6) nanocomposites with different R substitution amounts have been prepared by melt spinning and annealing process. The effects of R substitutions on the exchange-coupling range, effective anisotropy and coercivity were investigated. The experimental results show that Dy addition has no obvious influence on the exchange-coupling range for Nd8−xDyxFe87.5B4.5 nanocomposite. The monotonic increase of coercivity with increasing Dy content in this sample results mainly from the enhancement of anisotropy field by Dy addition. Substitution of Sm for Nd enlarges the exchange-coupling length notably. The coercivity of Nd8−xSmxFe87.5B4.5 increases with Sm content going through a maximum at x=0.3 and then decreases as x>0.3. This variation is owing to the increase of exchange-coupling range and the decrease of the anisotropy field with increasing Sm substitution amount.