Electric field control of structural, magnetic and transport properties of shape memory alloys: NiMnIn thin films at room temperature*

The goal of this work is to demonstrate a new family of nanoferroic multifunctional devices, based on shape-memory Heusler alloy films in ferroelectric heterojunctions, where resistance, magnetic and structural properties of the Heusler alloys will be switchable by applied electric field. Heusler alloys are a group of intermetallic compounds that have unique and interesting electro-magnetic behaviors, including the magnetic shape-memory effect. Selected shape-memory Heusler alloys are expected to be better than manganite-based compounds because their transformations can be controlled to occur near room temperature. This research attempts to distinguish the roles of electronic and strain-mediated coupling between layers in heterojunctions in order to determine the origin of each effect. It also attempts to identify the mechanism of the martensitic phase transformation in the Heusler alloy films. It is ultimately envisioned that this research may lead to a new class of nanoferroic multifunctional devices enabling new sensor and electronic applications. These devices will have a potential for use in memory, sensors and magnetic refrigeration.