Magnetostriction in some magnetic oxide compacted powders

Magnetostriction measurements have been made on a series of compacted powder samples of oxide pigments used in magnetic recording, to provide information for the evaluation of the role of magnetostriction in the recording process. Two composition series were measured at 294 K: one from γFe
2
O
3
through a range of partial reductions to Fe
3
O
4
, and another from 0 to 4 at. % Co in γFe
2
O
3
; also samples of CrO
2
. In addition, a 2 at. % Co-doped Fe
3
O
4
powder was measured as a function of field and temperature from 77 to 300 K. Magnetostriction was measured using a semiconductor strain gage on a rotating sample, in fields up to 9 kOe.