Effect of Ti addition on magnetic properties of TbCu 7 ‐type Sm‐Fe‐Co‐Mn system nitrides

To support the development of high‐performance isotropic bonded magnets, experiments were carried out to investigate the effect of Ti addition on the magnetic properties of Sm‐Fe‐Co‐Mn system nitride compounds with TbCu 7 ‐type structure. Sm 10 (Fe 0.9 Co 0.1 ) 89.5− x Mn 0.5 Ti x ( x =0 to 1.0) alloy ribbons were prepared by the single‐roller rapid‐quenching method. The effects of alloy composition and of heat treatment and nitriding conditions on the magnetic properties were examined. The optimum preparation conditions of the compounds were as follows. Composition: {Sm 10 (F 0.9 Co 0.1 ) 89 Mn 0.5 Ti 0.5 } 86.8 N 13.2 ; roller speed: 50 m/s; heat treatment: 700 ° C×60 min in high‐purity Ar gas; nitriding conditions: 420 ° C×15 h in high‐purity N 2 gas. Typical magnetic properties of the obtained compound powders were J r = 0.97 T, H cJ = 730.8 kA/m,( BH ) max = 140.0 kJ/m 3 (17.6 MGOe), T c=500 ° C. XRD, TEM photographs, and recoil loops of the hysteresis curve demonstrated that this sample had the characteristics of an exchange spring magnet. The value of ( BH ) max for the isotropic compression molding bonded magnet prepared from the {Sm 10 (F 0.9 Co 0.1 ) 89 Mn 0.5 Ti 0.5 } 86.8 N 13.2 powder was 94.8 kJ/m 3 (11.9 MGOe) at a bonded magnet density of 6.07 Mg/m 3 . The reversible temperature coefficient of J r was α( J r)=−0.04%/ ° C and the temperature coefficient of H cJ in the range from 25 ° C to 125 ° C obtained by linear extrapolation was α( H cJ)=−0.40%/ ° C. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(7): 25–31, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecj.10124