The mechanism of magnetization in materials Sm0.167Co0.833-xAlx

Abstract

Magnetization measurements are reported for homogeneous materials Sm_0.167Co_0.833-xAl_x both in bulk and 'oriented powder' form over a temperature range of 1.6-280K with fields up to 45 kOe. At cryogenic temperatures (4.2K) outstanding magnetic hardness is found in both the Al rich powder and the bulk specimen, with coercive forces, H_c, of order 40-50 kOe. This magnetic hardness decays with temperature according to a Curie type law. It is inferred from these findings that the domain wall energy increases strongly on Al substitution. Moreover, when Al is substituted for Co, the predominant mode of domain reversal changes at cryogenic temperatures from a mechanism involving domain wall nucleation to one of domain wall pinning. The mechanism of magnetization in highly energetic domain wall materials is shown to reflect in a delicate way details of structure on an atomic scale. Some preliminary results are presented for alloys Sm₂Co₁₇ and Sm₂Co₇ with Al substitution for Co. An exploratory effort at coating SmCo₅ powders with its Al substituted derivatives has been carried out via sintering with either Al or Sm-Al compounds. The potential for applications of Al derivatives of SmCo₅ in the fabrication process of permanent magnets is discussed.