The effects of intrinsic coercivity on the thermal stability of Sm(Co0.70Fe0.21Cu0.06Zr0.03)7.6 sintered magnets up to 450 °C

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Abstract
Sm(Co0.70Fe0.21Cu0.06Zr0.03)7.6sinteredmagnets with various H ci have been prepared by the conventional powder metallurgy method. Five magnets with H ci ranging from 15 to 40 kOe (at 25 °C) were selected to examine the impact of H ci on the irreversible loss and reversible temperature coefficient of induction (α). Magnets with higher H ci and Hk were found to exhibit lower irreversible losses when heated to 450 °C. Unlike the irreversible loss, α was found to be nearly independent of the H ci or Hk . These trends suggest that the irreversible loss is microstructure related and can be manipulated by process control, while α is more composition related and is dependent upon the overall chemical composition of the magnet.Br of 8.3 kG, Hc of 2.7 kOe, H ci of 3.5 kOe and BH max of 6.7 MGOe at 450 °C were obtained on a Sm(Co0.70Fe0.21Cu0.06Zr0.03)7.6magnet with a H ci of approximately 40 kOe at room temperature. Additional efforts are required to produce magnets which can be utilized at 450 °C.