FINAL REPORT: FG02-01ER-45906 - A novel class of artificially modulated magnetic multilayers based on magnetic shape memory alloys

摘要

The temperature dependent micromagnetic behavior, structural phase transitions, magnetic transition, and the dynamics of phase transitions have been investigated using magnetic shape memory alloys. Results provide a novel concept of ??polymagnets??. In thin film form the number of martensite variants is greatly reduced. A new technique to study dynamics of magnetic phase transitions has been developed applicable to bulk, thin films or multilayers. Transition pathways in magnetic shape memory alloys are as follows: Structural transitions followed by magnetic transition on cooling, and magnetic transition followed by structural transition on heating. The anisotropy of exchange spring mulilayers is greatly sensitive to substrate constraints, and shows a marked rotational hysteresis at lower temperatures. Results also show that a large reduction in coercivity of multilayers is a direct result of broadening of domain wall width by interlayer magnetostatic interactions.