Abstract
The realization of a controllable metamagnetic transition from AFM to FM ordering would open the door to a plethora of new spintronics based devices that, rather than reorienting spins in a ferromagnet, harness direct control of a materials intrinsic magnetic ordering. In this study FeRh films with drastically reduced transition temperatures and a large magneto-thermal hysteresis were produced for magnetocaloric and spintronics applications. Remarkably, giant controllable magnetization changes (measured to be as high has ~25%) are realized by manipulating the strain transfer from the external lattice when subjected to two structural phase transitions of BaTiO3 (001) single crystal substrate. These magnetization changes are the largest seen to date to be controllably induced in the FeRh system. Using polarized neutron reflectometry we reveal how just a slight in plane surface strain change at ~290C results in a massive magnetic transformation in the bottom half of the film clearly demonstrating a strong lattice-spin coupling in FeRh. By means of these substrate induced strain changes we show a way to reproducibly explore the effects of temperature and strain on the relative stabilities of the FM and AFM phases in multi-domain metamagnetic systems. This study also demonstrates for the first time the depth dependent nature of a controllable magnetic order using strain in an artificial multiferroic heterostructure.
Highlights
In this study samples were grown with the goal of inducing and stabilizing stresses in the system in order to maximize the films response to an external strain induced stimulus
A post anneal rapid thermal quench was implemented using a laser substrate heater after sputter deposition. This produces a giant magnetization response when subjected to the interfacial strain changes induced at two structural phase transitions of the BTO 001 single crystal substrate (orthorhombic (O) → rhombohedral (R) and orthorhombic → tetragonal (T))
These changes in magnetization occur at the structural phase transitions of the underlying BTO (001) single crystal substrate
Summary
In particular PNR shows that this change happens almost solely in the bottom half of the film; effectively inducing a massive transformation of most of the remaining AFM phase to FM ordering (Fig. 2(e)) This is in direct agreement with reports that tensile strain of FeRh induced by growth on different lattice mismatch engineered substrates stabilizes the FM phase by lowering the transition temperature[32,33]. The present findings provide a new discovery of a strong strain mediated handle for the control of magnetic ordering in FeRh films, and suggests exploring similar coherent material systems that can be implemented in thin film form
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