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Phosphorus substituted (Pr,Tb)8(Fe,Nb,Zr,P)88B4 nanocomposites have been produced by melt-spinning. The effects of phosphorus substitution as well as wheel speed on the crystallization behavior and magnetic properties of the melt-spun samples have been investigated. With the substitution of phosphorus, the crystallization temperature of amorphous phase increases. The optimum wheel speed was found to be around 25 m/s for as-spun ribbons and 40 m/s for the annealed samples, both of which present excellent second quadrant hysteresis loop shapes due to the fine grain size of α-Fe which is around 20 nm. The addition of phosphorus also greatly improves the coercivity of Pr–Fe–B nanocomposites without a significant loss of saturation magnetization. A higher coercivity of 9.2 kOe in P-substituted samples was obtained as compared to 8.1 kOe in P-free samples. This is attributed to a narrower temperature span between the crystallization into TbCu7 structure and the transformation into the 2:14:1 phase caused by the phosphorus substitution.

Exchange-coupled nanocomposites have attracted considerable attention due to their potential application for high performance permanent magnets [1,2]. The melt-spinning method is a potential way to fabricate anisotropic nanocomposite magnets. The microstructural changes that occur in melt-spun ribbons during solidification, especially, from the contact side (wheel side or roll side) to the free surface of the ribbons can give rise to a preferred orientation. Thus, crystallographic texture may be introduced into the ribbon samples, which may lead to the formation of anisotropic nanocomposite magnets, with much improved magnetic properties [3,4].