Effect of Important Factors on Temperature Variation of Coercivity in Sr-La-Co High-Performance Sintered Ferrite Magnets

The authors varied the composition of Sr
_1-x
La
_x
Fe
_12-x
Co
_x
O
₁₉
sintered ferrite magnets (
x
=0-0.4) for analyzing the effects of various factors on the temperature variation of coercivity (
H
_cJ
) in the temperature range between 173 and 423 K, where
x
is the substituted amount. The effects of the crystal grain size (
C
_t
), the mechanism of magnetization reversal (
R
_h
), the degree of crystal grain orientation (OD), and the anisotropy field (
H
_A
) on the temperature variation of
H
_cJ
were also examined. It was confirmed that the equation
H
_cJ
=
C
_t
(0.4/
R
_h
) OD (
H
_A
-
H
_d
-
H
_in
) was applicable for expressing the measured
H
_cJ
in a wide temperature range between 173 and 423 K for all the magnets, where
H
_d
and
H
_in
are the demagnetizing field of shape anisotropy and the interaction field between crystal grains, respectively. Above all, the factors of
C
_t
,
R
_h
, and
H
_A
had significant effects on the temperature variation of
H
_cJ
for all the magnets.