Magnetic and magnetostrictive properties of manganese substituted cobalt ferrite

The magnetic and magnetostrictive properties of polycrystalline Co 1− x Mn x Fe 2 O 4 (0 ⩽ x ⩽ 0.4) have been studied. Although the Curie temperature decreases continuously with increasing concentration of Mn, the magnetization remains high up to x = 0.3 and unexpectedly low coercivity is observed for this composition showing an unusual magnetostrictive behaviour. This composition shows a relatively larger magnetostriction at low fields. Moreover, the strain derivative which is the slope of the magnetostriction curve at low magnetic fields is almost doubled and the field at which maximum magnetostriction is observed is reduced to almost half for 30% of Mn substitution. The results show that x ≈ 0.3 in Co 1− x Mn x Fe 2 O 4 is an optimum composition with superior magnetostrictive properties for many applications.