Magnetic properties of rapidly quenched (Nd2Fe14B)1−x(N d1.1Fe4B4)x alloys

Abstract Amorphous ribbons with the formal composition (T 1 ) 1− x (T 2 ) x (i.e. Nd 12±ϵ Fe 88 − y B y ) with T 1 = Nd 2 Fe 14 B and T 2 = Nd 1.1. Fe 4 B 4 and 0≤ x ≤1.0 were prepared by a single roller quenching apparatus. The Curie temperature T c and crystalliz ation temperature T cr of the samples and the effects of heat treatment on their magnetic properties and microstructure were studied. The concentration dependence of T c is found to have a maximum value of 505 K and about x = 0.19 ( y = 13). The T cr increases rapidly with increasing x , goes through a maximum to lower values, then rises again. The X-ray diffraction measurements show that the crystallized samples consist of T 1 and T 2 . In the electron diffraction microscope we see well defined grains of T 1 and T 2 which have an average size of about 650 A for T 1 and about 1500 A for T 2 after annealing at 700–800°C. The coercivity under optimal annealing condition is found to be approximately constant with increasing concentration x of the nonmagnetic T 2 phase. An intrinsic coercivity of 8.6 kOe and an energy product of 12 MGOc in Nd 2 Fe 14 B are obtained at room temperature by annealing at 800°C for 10 min.