High-field magnetization process and spin reorientation in (Nd1-xDyx)2Fe14B single crystals.

Abstract

The high-field magnetization process in the (${\mathrm{Nd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Dy}}_{\mathit{x}}$${)}_{2}$${\mathrm{Fe}}_{14}$B system has been investigated using single crystals with x=0, 0.125, 0.2, 0.33, 0.47, 0.6, and 1. Magnetization measurements were performed using steady magnetic fields of up to 300 kOe generated by a hybrid magnet system and pulsed magnetic fields of up to 400 kOe. When the field was applied along the [100] direction at low temperatures, the first-order magnetization process (FOMP) was observed in the samples with x=0.125, 0.2, and 0.33 as well as in ${\mathrm{Nd}}_{2}$${\mathrm{Fe}}_{14}$B (x=0). The field ${\mathit{H}}_{\mathit{j}}$ where the FOMP occurred was found to increase rapidly with increasing x, reaching 320 kOe for the sample with x=0.33 at 4.2 K. The spin-reorientation temperature (${\mathit{T}}_{\mathrm{SR}}$), below which the magnetic moment tilted from the [001] to the [110] direction, was determined from ac susceptibility measurements. The ${\mathit{T}}_{\mathrm{SR}}$ decreased with increasing x. The tilting angle \ensuremath{\theta} at 4.2 K also decreased gradually with increasing x. Magnetization curves of this mixed system were calculated by assuming the crystalline-electric-field parameters for the two end members. The observed concentration dependence of ${\mathit{H}}_{\mathit{j}}$ and \ensuremath{\theta} as well as the magnetization curves were successfully reproduced by this simple calculation.