Nanoscale manipulation of magnetic domains by interfacial strain-induced proximity

Abstract

Coupling lattice and spin degrees of freedom without the use of external magnetic fields allows for energy-efficient spintronic devices. In this context, hybrid materials composed of an oxide layer undergoing a first-order, structural phase transition (SPT), such as V2O3, and a ferromagnetic layer, such as Ni, constitute a very promising paradigm for the development of such applications. In the case of a Ni/V2O3 heterostructure, the structural domains inherent to the first-order phase transition in the V2O3 cause a differential strain pattern in the Ni layer. By virtue of the inverse magnetorestrictive effect, this strain pattern is converted into a magnetic anisotropy distribution in the Ni. This offers a promising alternative to voltage-controlled magnetism or other switching mechanisms without a magnetic field [1,2].Here we show by direct imaging of the thermal evolution of the Ni spin structure that the magnetic domains can be tuned in both size and orientation upon crossing the structural phase transition (SPT) of the proximal V2O3 layer [3]. We find a drastic temperature-driven reorientation of the Ni magnetic domains across the SPT which is responsible for an abrupt increase in the coercive field (up to 500%). By synchrotron-based X-ray microscopy we show a reconfiguration of the ferromagnetic domain pattern in the Ni layer across the V2O3 SPT together with changes in magnitude and direction of the magnetic anisotropy. These observations are in good agreement with both angular dependent ferromagnetic resonance measurements and micromagnetic simulations. Our simulations successfully replicate the change in the coercivity as well as the reorientation of the magnetization of the Ni domains after the implementation of a simple model of strain-dependent magnetic anisotropies. Furthermore, simulations also exhibit a phase coexistence of different magnetic domains across the SPT in the V2O3. Direct observations of the lateral correlation length of the Ni domains show an increase of almost an order of magnitude at the SPT compared to room temperature as well as a broad spatial distribution of the local transition temperatures. This corroborates the phase coexistence of Ni anisotropies due to the V2O3 structural domains coexistence across the SPT. Our data reveal that the reorientation of Ni domains is controlled by the reconfiguration of the structural domains of the oxide layer across the SPT [4,5], due to strain induced proximity.Our findings reveal a novel pathway to control magnetic domains without a magnetic field through proximity to a material undergoing a first-order structural phase transition, which allows for engineering of coercive fields for novel data storage architectures and novel device concepts based on “straintronics”. Acknowledgements:This work was supported by the Spanish MINECO projects MAT2015-68772-P and PGC2018-097789-B-I00 and European Union FEDER funds. A.F.R. and M.G.M acknowledge financial support from the EU CALIPSO Transnational Access programme. J.G.R. acknowledges support from Colciencias under grant 120471250659. The work by I.V., C.W. and I.K.S. at UCSD were supported by the Office of Basic Energy Science, U.S. Department of Energy, BES-DMS funded by the Department of Energy’s Office of Basic Energy Science, DMR under grant DE FG02 87ER-45332. **