Estimation of texture and anisotropy field in a NdDyFeCoB magnet by magnetic measurements at the perpendicular direction

Abstract

A reliable method for estimating the anisotropy field in samples with uniaxial texture distribution is presented and discussed. From experimental measurements of the hysteresis in VSM (Vibrating Sample Magnetometer) at the parallel and perpendicular direction (using as reference the direction of alignment of the sintered magnet), and with the simultaneous fitting of the 1st quadrant in the region of reversible rotation of the measured hysteresis, the anisotropy field, magnetization of saturation and the crystallographic texture were determined. The examined magnet was a NdDyFeCoB magnet, with the proportion between the 5 main alloying elements represented by the atom% formula: (Nd8.6Dy4.9)(Fe81,1Co4,1Cu1,3). The crystallographic texture of the magnet can be described by a Gaussian distribution. It was found Mr/Ms = 0.969 representing the crystallographic texture of the magnet. The anisotropy field of the examined (NdDy)(FeCoCu)B sample was estimated as 111 kOe. The coercivity of the sample is very high, 43.8 kOe. The coercivity is 63.6% of the theoretical maximum predicted by the anisotropic Stoner-Wohlfarth Model.