Pubblicazioni

Versione: 1.0 Approvato

LDO-ID 2020-10-16-05

Titolo Theoretical model of strain perturbed resistivity in granular manganese perovskite systems

Abstract

Perovskite-like compounds have been the subject of intense research works in the last decades, due to their interesting and many-fold fundamental physical properties which have suggested a large variety of possible practical applications. This class of materials is characterized by a particular rich phase diagram, with the coexistence of different forms of order involving several degrees of freedom such as charge, spin, orbital and crystal lattice, finally resulting in nano-scale phase separation and intrinsic inhomogeneity. The consequent possibility to change the physical behavior of these compounds, by playing with several factors (as the ionic size, the chemical composition, the applied magnetic field, the external strain etc.) has burst the interest in investigating their possible use in various devices. Furthermore, the balance between competing phases could be so delicate that small changes in these factors could be related to large changes in their physical properties. By large, the most studied perovskite families, are those of cuprates and manganites, due to the observed phenomena of High-Temperature Superconductivity HTS (cuprates) and colossal magneto-resistivity CMR (manganites). In the case of manganites, the CMR effect is traced back to a paramagnetic-ferromagnetic transition which, thanks to the double-exchange mechanism, simultaneously opens a conduction channel among aligned Mn electronic spins. This is another clear evidence of the strong interplay, in these compounds, among different orders at a nanometre scale. Moreover, the dependence on the chemical composition of the Curie temperature below which the spin alignment appears, has open the way to studies of their possible use in spin valve and spin filter devices. The tight relation between the electrical transport behavior, the Curie temperature and the externally applied strain in manganites, has also suggested to investigate this interplay in view of future applications. Theoretical prediction of the effect of biaxial strain on the electrical and magnetic properties of crystalline manganites [ref Millis] have been confirmed experimentally [ref. Adamo]. The main physical effect taken into account in these studies, was the crystal lattice distorsion due to the externally applied biaxial strain and its effect on the double exchange mechanism and, finally, on the Curie temperature values. For these reasons, both the theoretical and the experimental works, have been related to manganite epitaxial thin films, implying stiff single crystal substrates, which do not have large commercial use. The deposition of manganite thin films on poly-crystalline substrates, typically results in granular systems. In granular thin films, the externally applied strain no longer directly influences the crystal lattice, but it is generally incorporated by changing the grain arrangement. The scientific literature about the strain effects on the electrical transport properties of manganites is largely related to studies of epitaxial thin films and the researches involving the effects on manganite granular systems are very rare. The aim of this work is to investigate the sensitivity to the strain tensor of a manganite granular system. In particular, implementing the theoretical model proposed by Zhang et al., we have been able to describe the effects of externally applied deformations on the electrical resisistivity of the systems. Our results show that the resistivity changes are appreciable even for small distorsions. The limits and the potential developments of our work are also discussed.

Autori De Feo Pasquale, Ferraioli Fabrizio, Coppola Nunzia, Maritato Luigi

Tipologia Paper for Specialistic Magazine

Media Coatings Journal - Special Issue on "Advances in Perovskite Thin Films" (MDPI AG)

Sito web

https://www.mdpi.com/journal/coatings/special_issues/advance_perovskite_thin_filims

Anno 2020