The influence of grain size and impurities on the magnetic properties of the soft magnetic alloy 47.5% NiFe

An attempt has been made to equate quantitatively the coercive force as a function of the grain size and the concentration of nonmagnetic inclusions. It was found that the coercive force H
c
of recrystallized 47.5% nickel-iron can be completely described, independent of the final anneal temperature, by the grain size d
K
and the inclusion content N
F
. Only nonmagnetic inclusions of sub-micron size (0.02- 0.5 μm) were found to be of significance. A definite correlation between the coercive force of 47.5% nickel-iron and those inclusions visible using an optical microscope (> 1μm) was not observed. Furthermore, there was no clear dependence of the coercive force on the sulfur and oxygen content. The grain size term H
cK
was found to be in good agreement with the theory of A. Mager [1]. Surprisingly, there was no difference between the low-angle grain boundaries of strip with cube texture and the large-angle grain boundaries of un-textured strip with respect to H
cK
.