Evolution of magnetic domain patterns associated with field-induced DHCP-HCP transformation of Co-1.2%Fe alloy

The magnetic domain patterns of the pure double-hcp (dhcp) phase and hcp-mi xed-dhcp phase of Co-1.2%Fe alloy single crystals were investigated to clar ify the nucleation and growth process of the hcp phase from the dhcp phase in the external magnetic held. The thin hcp phases appeared to be parallel to the c-plane in the pure dhcp phase at phase transformation. The domain o bservation failed to detect the nucleation site of the dhcp-to-hcp phase tr ansformation. The nucleation site and growing process of the hcp phase are discussed with respect to the effect of the shear stress induced by magneto striction. The calculated maximum shear stress induced by magnetostriction was found to be on the same order of the resolved shear stress of Co, and i t could be realized in the domain walls but not in the domains. This shear stress in the domain walls might be the motivating force in generating nucl eation sites of hcp phase.