HIGH-TEMPERATURE MAGNETIC-PROPERTIES OF TBCU7-TYPE SMCO-BASED FILMS

In applications where large remanent moments and energy products are r equired at elevated temperatures, SmCo-based permanent magnets provide the best properties. In addition to their high Curie points, these Sm Co-based ordered phases of 1-5, 2-17, and the disordered 1-7 phase sho w large uniaxial anisotropies at elevated temperatures. We have now me asured the high-temperature hysteresis properties of single-phase TbCu 7-type SmCo-based permanent magnet films. Such single-phase samples ha ve the advantage that optimal magnetic properties can be obtained from the as-sputtered films without any subsequent heat treatments. Normal ly bulk samples in this composition range form the two phase cellular structure whose magnetic properties are very sensitive to heat treatme nts. Single-phase TbCu7-type films of composition Sm13Co58Fe20Cu7Zr2 w ere sputter synthesized such that the crystallite c axes were oriented in the film plane. The net anisotropy field of the films remained lar ger than the maximum applied field of 18 kOe even at the highest measu rement temperature of 460 degrees C. Thus all measurements were from m inor hysteresis loops. The in-plane coercivity showed a monotonic decr ease from 6.0 kOe at room temperature to 1.3 kOe at 460 degrees C. The in-plane remanent flux density decreased from 8.5 kG at 50 degrees C to 5.8 kG at 460 degrees C. (C) 1996 American Institute of Physics.