5–7 Dec 2018
CERN
Europe/Zurich timezone

Perturbed Angular Correlation γ-γ measurements on Naturally Layered Perovskites Ca_{n+1}Mn_{n}O_{3n+1}

5 Dec 2018, 14:45
15m
503/1-001 - Council Chamber (CERN)

503/1-001 - Council Chamber

CERN

162
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Speaker

Pedro Miguel Da Rocha Rodrigues (Universidade do Porto (PT))

Description

Magneto-electric multiferroics form an attractive class of materials, not only for the diversity of exciting fundamental phenomena they present but also by the potential technological applications foreseen. Among them are energy efficient memory devices, multiple state memories, as well highly sensible electrical-magnetic field sensors. Although the research in this area has increased dramatically in the last years, the number of systems presenting magnetoelectric coupling at room temperature is still very scarce.

Naturally layered perovskites (NLP) such as the Ruddlesden-Popper (R.P.) phases ($A_{n+1}B_{n}O_{3n+1}$) have appeared as a fascinating route to achieve nonexpensive room temperature multiferroic materials. In these NLP, distortions of the lattice such an $BO_{6}$ octahedron rotation and tilting modes couple to polar cation dislocation modes inducing a ferroelectric polarization, in a mechanism known as hybrid improper ferroelectricity. The novel idea behind these NLP is that the ferromagnetic and ferroelectric orders can be coupled through the same lattice instability, providing an indirect but very strong magneto-electric coupling.

Perturbed Angular Correlation γ- γ (PAC) hyperfine technique offers a unique opportunity to probe at the local scale the structural, charge and magnetic phase transitions of these NLP systems. At ISOLDE-CERN, by using metastable $^{111m}Cd$ isotopes as radioactive probes, PAC measurements were performed in a extensive range of temperatures (1150K - 11K), namely on the prototypical hybrid improper ferroelectric and novel multiferroic $Ca_{3}Mn_{2}O_{7}$, as well of its homologous non polar $Ca_{2}MnO_{4}$ and $CaMnO_{3}$ R.P. compounds. Combined Ab-initio electronic structure calculations in the framework of the Density Functional Theory (DFT) were also performed to understand and show how the measured Electrical Field Gradients at the Cd probing sites are sensitive to the $BO_{6}$ octahedron distortion modes present in these compounds.

Primary authors

Pedro Miguel Da Rocha Rodrigues (Universidade do Porto (PT)) Mr Tiago Leal (University of Porto) Goncalo De Pinho Oliveira (Universidade do Porto (PT)) Mr Ricardo Moreira (University of Porto) Ricardo Cesar Carvalho Teixeira (Universidade do Porto (PT)) Mr Ivan de Paula Miranda (University of São Paulo) Dr Samuel Santos (University of São Paulo) Prof. Lucy Credidio Assali (University of São Paulo) Prof. Helena Maria Petrilli (University of São Paulo) Joao Martins Correia (Universidade de Lisboa (PT)) Armandina Maria Lima Lopes (Universidade do Porto (PT)) Prof. Joao Pedro Esteves De Araujo (Universidade do Porto (PT))

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