Effect of Ti Addition on Magnetic Properties of TbCu₇-type Sm-Fe-Co-Mn System Nitrides

Abstract

This experiment was aiming for making high performance isotropic bonded magnet. And this experiments were carried out to investigate the effect of Ti addition for magnetic properties of Sm-Fe-Co-Mn system nitriding compounds with TbCu₇-type structure. Sm₁₀(Fe_0.9Co_0.1)_89.5-xMn_0.5Ti_x (x = 0˜1.0) alloy ribbons were prepared by the single roller rapid-quenching method. And the effects of alloy composition, and conditions of heat-treatment and nitrogenation on the magnetic properties were examined. The optimum preparation conditions of the compounds are as follows. Composition: {Sm₁₀(Fe_0.9Co_0.1)₈₉Mn_0.5Ti_0.5}_86.8- N_13.2, roller velocity: 50 m/s, heat treatment: 700 °C×60 min in high-purity Ar gas, and nitriding condition: 420 °C×15 h in high-purity N₂ gas. Typical magnetic properties of the obtained compound powders are J_r = 0.97 T, H_cJ = 730.8 kA/m, (BH)_max = 140.0 kJ/m³ (17.6 MGOe), and T_C = 500 °C. It was found that this sample was an exchange spring magnet from XRD, TEM photograph and recoil loops of the hysteresis curve. The value of (BH)_max for the isotropic compression molding bonded magnet prepared from the {Sm₁₀(Fe_0.9Co_0.1)₈₉Mn_0.5Ti_0.5}_86.8N_13.2 powder is 94.8 kJ/m³ (11.9 MGOe), when the density of bonded magnet is 6.07 Mg/m³. And the reversible temperature coefficient of J_r is α(J_r) = -0.04 %/°C, the temperature coefficient of H_cJ in the range from 25 °C to 125 °C obtained by a linear extrapolation is α(H_cJ) = -0.40 %/°C.