Magnetic properties of nanocomposite Pr₂(FeCo)₁₄B/α-(FeCo) with addition of Sn

Ribbons of nanocomposite Pr₂(FeCo)₁₄B/α-(FeCo) with an additive of low melting point metals, such as Al, Zn, Sn or In, were prepared by melt spinning. It was found that the remanence could be obviously improved at the expense of coercivity by the addition of Sn. The remanence J_r about 1.30 T and maximum energy product (BH)_max about 20.5 MG Oe were obtained in Pr₉Fe₇₄Co₁₂B₅ doped with 0.5% Sn, while J_r and (BH) in the ribbons without the additive were about 1.17 T and 17.9 MG Oe, respectively. The additive Sn is located at the grain boundaries rather than in grain interior in the ribbons. The obvious improvement of the remanence originates from the refinement of the microstructure and the increase of soft phase content by the addition of Sn. The effect of additive Sn on the coercivity was also discussed. By increasing the content of the magnetically hard phase, the intrinsic coercivity _iH_c can be elevated. Thus, the optimum magnetic properties, such as J_r = 1.27 T, _iH_c = 5.7 kOe and (BH)_max = 22.5 MG Oe, were obtained in Pr_9.5Fe_73.57Co_11.93B₅ ribbons doped with 0.5% Sn.