Functional lattice instabilities in naturally layered perovskites

Abstract

Room temperature magneto-electric (ME) compounds are very rare and high-quality artificially layered ones are in general difficult and costly to produce. Naturally Layered structures (NLP) offer, in this respect, an inspiring alternative route to achieve non-expensive and high performance room temperature MEs. Moreover, such materials offer also functionalities like negative thermal expansion enlarging vastly application potential. Here, the study of NLP like structures, aiming new functional materials for sustainable energy and health applications, is envisaged. The project relies on two interrelated pathways, viz: 1) Using the huge potentialities, yet not fully explored, of NLP, this project will develop new systems with enhanced room temperature cross-coupled response. The manipulation of acentricity will be achieved by means of rotations of oxygen octahedra and cation site order. For this, the main vectors will be the incorporation of multiple cations into Ca3(Mn,Ti)2O7 and AA BMnO6 lattices, strain engineering and high pressure, thus adjusting lattice, electric and magnetic interactions. 2) Using a set of complementary techniques including singular local probe ones a comprehensive study on the competition/cooperation between spin, charge and orbital degrees of freedom, as well as their complex linkage to lattice instabilities and functional coupling effects is envisaged. The relevant properties in these materials are typically correlated to local landscapes that are not well described by long-range crystallographic/magnetic average models. By determining the atomic scale details leading to spontaneous ferroic orders via local probe techniques, new strategies to manufacture novel functional structures will materialize. DFT calculations will build on the understanding on how ferroic orders might arise and will assist in the atomic scale-up of new multiferroics.The team is a balanced mix of senior and highly motivated young PhD students and relies on a long-standing collaboration on material?s research exploring expertise/techniques complementarity, now joined together to develop new NLP functionalities. Traditional methods for bulk sample production are available at FCUP, and will be complemented by Metastable bulk ones at Institute Neel and thin film production at Minho Univ. A plethora of techniques for extended physical studies are available at the proponent institution (PI), recently reinforced by the approval of the Network of Extreme conditions Laboratories-NECL leaded by the PI(Portugal) under the National(Portuguese) Roadmap of Research Infrastructures. Local probe studies are also expected at ISOLDE CERN and Oak Ridge National Lab. Finally DFT calculations will be performed by the São Paulo Univ. team and supported by Dr. Stroppa at CNR-SPIN L?Aquila. By the materials here produced and the knowledge generated, this research will decisively contribute to improve room temperature magneto-electric materials and devices (AU)