Investigation of thermal stability at 300-550 degreesC for the newly develo
ped Sm(CowFevCuxZry)(z) high temperature magnets is reported in this paper,
Three Factors are responsible for the irreversible losses at high temperat
ures, One factor is the loss associated with a nonlinear induction demagnet
ization curve, This results in significant loss when the magnet is exposed
to temperatures higher than the maximum use temperature T-M. Another factor
is the surface oxidation, which is more severe with increasing temperature
and time at high temperature. Surface oxidation can be reduced by coating
with a high temperature ceramic coating, The third factor is the result of
metallurgical changes in the magnets. This loss is relatively small in the
new magnets, which actually is < 2% after 360 hours at 550<degrees>C. The e
xperiment confirms that coated magnets with T-M upw to 550 degreesC can be
expected to have considerable life expectancy and relatively low losses at
the intended T-M.