Speaker
Ricardo Cesar Carvalho Teixeira
(IFIMUP and IN-Institute of Nanoscience and Nanotechnology, University of Porto; CFNUL - Centro de Física Nuclear, University of Lisbon)
Description
In the last years, a deep focus has been devoted to manganites and their exquisite properties triggered by the interplay of spin, orbital, charge and structural degrees of freedom, driven by both fundamental interest and possible applications on colossal magnetoresistance, magnetocaloric and multiferroic properties [1,2]. Additionally, low-cost AMnO3, as well as its doped counterparts, have shown promising results for catalyst solutions [3]. In these systems orbital occupancy of the metal ion, orbital order and the Jahn-Teller effect play a critical role on the material's macroscopic properties.
In this work, a Perturbed Angular Correlation (PAC) study on the RMnO3 (R=Sm, Nd, Pr, La) system is presented, showing a linear increase of the main component (Vzz) of the Electric Field Gradient (EFG) with the rare-earth ionic radius. These results are compared with ab initio density functional theory calculations, carried out also in the framework of this study. Different values of the on-site Coulomb parameters were used in the calculations in order to better reproduce the experimental results.
Additionally, the EFG temperature evolution was studied at the La site for the prototype LaMnO3 system across the Jahn-Teller and concomitant orbital order/disorder transition. Unexpectedly, a drastic change in the EFG parameters was observed at temperatures much below the Jahn-Teller transition, pointing to a new characteristic temperature in this system. This result gives further proof of the recently reported [4,5] partial melting of the system's orbital order occurring in this system at temperatures much below the order/disorder transition.
1. Magnetic and magnetoelectric excitations in multiferroic manganites, A M Shuvaev, A A Mukhin and A Pimenov, J. Phys.: Condens. Matter 23 113201 (2011)
2. Electric Field Control of Terahertz Polarization in a Multiferroic Manganite with Electromagnons, A. Shuvaev, V. Dziom, Anna Pimenov et al., Phys. Rev. Lett. 111, 227201 (2013)
3. Design principles for oxygen-reduction activity on perovskite oxide catalysts for fuel cells and metal–air batteries, J. Suntivich, H. Gasteiger, N. Yabuuchi et al., Nature Chemistry 3, 546–550 (2011)
4. Melting of the orbital order in LaMnO3 probed by NMR, A. Trokiner, S. Verkhovskii, A. Gerashenko et al, Phys. Rev. B 87, 125142 (2013)
5. ESR evidence for partial melting of the orbital order in LaMnO3 below the Jahn-Teller transition, S. Schaile, H.-A. Krug von Nidda, J. Deisenhofer et al, Phys. Rev. B 90, 054424 (2014)
Author
Ricardo Cesar Carvalho Teixeira
(IFIMUP and IN-Institute of Nanoscience and Nanotechnology, University of Porto; CFNUL - Centro de Física Nuclear, University of Lisbon)
Co-authors
Armandina Maria Lima Lopes
(IFIMUP and IN-Institute of Nanoscience and Nanotechnology, University of Porto)
Goncalo De Pinho Oliveira
(IFIMUP and IN-Institute of Nanoscience and Nanotechnology, University of Porto; CFNUL - Centro de Física Nuclear, University of Lisbon)
Joao Martins Correia
(Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, University of Lisbon)
Joao Nuno Santos Goncalves
(CICECO and Department of Physics - University of Aveiro)
Joao Pedro Esteves De Araujo
(IFIMUP and IN-Institute of Nanoscience and Nanotechnology, University of Porto)
Juliana Schell
(Universitaet des Saarlandes (DE))
Marcelo Baptista Barbosa
(IFIMUP and IN-Institute of Nanoscience and Nanotechnology, University of Porto)
Tania Manuela De Melo Mendonca
(CERN)
