High-temperature magnetic properties of TbCu7-type SmCo-based films

Abstract

In applications where large remanent moments and energy products are required at elevated temperatures, SmCo-based permanent magnets provide the best properties. In addition to their high Curie points, these SmCo-based ordered phases of 1-5, 2-17, and the disordered 1-7 phase show large uniaxial anisotropies at elevated temperatures. We have now measured the high-temperature hysteresis properties of single-phase TbCu7-type SmCo-based permanent magnet films. Such single-phase samples have the advantage that optimal magnetic properties can be obtained from the as-sputtered films without any subsequent heat treatments. Normally bulk samples in this composition range form the two phase cellular structure whose magnetic properties are very sensitive to heat treatments. Single-phase TbCu7-type films of composition Sm13Co58Fe20Cu7Zr2 were sputter synthesized such that the crystallite c axes were oriented in the film plane. The net anisotropy field of the films remained larger than the maximum applied field of 18 kOe even at the highest measurement temperature of 460 °C. Thus all measurements were from minor hysteresis loops. The in-plane coercivity showed a monotonic decrease from 6.0 kOe at room temperature to 1.3 kOe at 460 °C. The in-plane remanent flux density decreased from 8.5 kG at 50 °C to 5.8 kG at 460 °C.

Metastable phases in rare-earth permanent-magnet materials

“…Amorphous, CaCu 5 -, Th 2 Zn 17 -and TbCu 7 -type SmCo-based films were synthesized by sputtering (Chen et al 1993, Rani et al 1997. Single phase TbCu 7type films of composition Sm 13 Co 58 Fe 20 Cu 7 Zr 2 were sputter synthesized such that the crystallite c-axes were oriented in the film plane (Hegde et al 1996). The magnetic and crystallographic properties of these films as a function of sputter deposition parameters were studied by Hegde et al (1994).…”

“…In addition to their high Curie temperatures, the SmCobased amorphous films as well as the SmCo-based ordered phases of 1:5, 2:17, and the disordered 1:7 phase show large uniaxial anisotropies at elevated temperatures (Chen et al 1993, Hegde et al 1994, Rani et al 1997. The advantage of the single phase TbCu 7 -type SmCobased permanent magnet films is that optimal magnetic properties can be obtained from the as-sputtered films without any subsequent heat treatments (Hegde et al 1996). The net anisotropy field of the films remained larger than the maximum applied field of 18 kOe even at the highest measurement temperature of 460 • C. The in-plane coercivity showed a monotonic decrease from 6.0 kOe at room temperature to 1.3 kOe at 460 • C. Figure 26 show magnetic hysteresis loops at 50 • C, for measurements inplane and perpendicular to the file plane.…”

Thermal stability of metastable, epitaxial PrCo7films with high energy density

“…RE-Co (RE = rare earth) magnets have attracted the magnetic community since their discovery in the late 1960s because of their fascinating intrinsic and extrinsic magnetic properties. Owing to the high Curie temperature, RE-Co compounds with high cobalt content take a leading role in the development of permanent magnets for high temperature applications, which has been intensified in recent years [1][2][3][4][5][6][7]. Among the RE-Co family, the RECo 7 structure (TbCu 7 type) often possesses the best combination of intrinsic properties (high Curie temperature T C , high uniaxial anisotropy and high saturation polarization) and is thus an obvious choice for permanent magnet development.…”

C-5 Absolute Thickness Determination of SMCO Films on Silicon Substrates Utilizing X-ray Diffraction and Their Composition Measurements By EXRF

“…The SmCo based films had a nominal composition of Sm 0.13 Co 0.58 Fe 0.20 Cu 0.07 Zr 0.02 . (Hegde 1996) This composition for bulk magnets corresponds to that normally designated as SmCo 2-17 magnets. (Parker, 1990) When films are directly crystallized onto heated substrates with this composition it has been extensively shown that the films can be formed as a single phase deposit with the TbCu 7 -type structure.…”