Stress demagnetization in magnetic coated disks

When mechanical forces are applied to acicular particles that are dispersed in a magnetic coated disk, the resultant stress anisotropy energy produces the magnetization inversion, which is called stress demagnetization (abbreviated to S.D.). We exhibited various tendencies on S.D. in some coatings containing γFe
2
O
3
, Fe
3
O
4
, Co-γFe
2
O
3
, Co-Fe
3
O
4
and metallic Fe-Co powder, respectively. And we suggest a possible S.D. mechanism. S.D. has proved to be an inverse magnetostrictive effect with some problems solved. According to the present model, each kind of powder is shown to have various S.D. ratios, depending on its values of a kind of a magnetostriction constant
\lambda*
and a ratio of a magnetostriction energy to a shape anisotropy energy
K\sigma/Ku
. Metallic Fe-Co powder, for example, has no S.D., since inverse magnetostriction effect is supposed not to be induced owing to its large saturation magnetization despite its large
\lambda*
, i.e.,
K\sigma/Ku < 1
.