Effect of oxygen stoichiometry on the energy of CEF levels in Pr 2 NiO 4.25

Journal of Physics Conference Series, vol. 3161, pp. 012020

Abstract

Abstract In this work, we present a study of the CEF environment in Pr 2 NiO 4+δ (δ = 0.25), through the analysis of inelastic neutron scattering measurements combined with point charge model simulations. Inelastic neutron scattering experiments on Pr 2 NiO 4.25 were conducted using the thermal triple-axis spectrometer IN20 at the Institut Laue-Langevin. An inelastic peak was observed at 5.58 meV, which shifted to 6.30 meV upon lowering the temperature to 1.5 K. At 300 K, no peak was observed within this energy transition range. Using point charge model calculations, we analysed the crystal electric field effects on the energy levels of the Pr 3+ magnetic ions. The CEF calculations, performed with the PyCrystalField program, provided an approximate understanding of the CEF environment of the over-stoichiometric Pr 2 NiO 4.25 . The calculations showed that the strong peak seen at low temperatures in inelastic neutron scattering experiments comes from two singlets corresponding to the first energy levels of the Pr 3+ sites without interstitial oxygen. While the first transition for the Pr 3+ with interstitial as ligand shows an energy much lower, close to the elastic line that barely we could resolve in our scans. Moreover, the calculations revealed a strong link between the position of the first energy transition peak and the Pr-O ap atomic distances.

Authors 7

1. Laura Zeni Cunha

   Centre National de la Recherche Scientifique · Université de Montpellier · École Nationale Supérieure de Chimie de Montpellier · Institut Charles Gerhardt Montpellier · Institut Laue-Langevin

   Affiliation as printed

   ICGM, Univ. Montpellier, CNRS, ENSCM, Montpellier 34000, France

   Institut Laue-Langevin (ILL), 71 Avenue des Martyrs, 38042 Grenoble, France

2. Andrea Piovano

   Institut Laue-Langevin

   Affiliation as printed

   Institut Laue-Langevin (ILL), 71 Avenue des Martyrs, 38042 Grenoble, France

3. Martin Boehm

   Institut Laue-Langevin

   Affiliation as printed

   Institut Laue-Langevin (ILL), 71 Avenue des Martyrs, 38042 Grenoble, France

4. Monica Ceretti

   Centre National de la Recherche Scientifique · Université de Montpellier · École Nationale Supérieure de Chimie de Montpellier · Institut Charles Gerhardt Montpellier

   Affiliation as printed

   ICGM, Univ. Montpellier, CNRS, ENSCM, Montpellier 34000, France

5. Wolfgang Schmidt

   Forschungszentrum Jülich · Institut Laue-Langevin

   Affiliation as printed

   Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at ILL, 71 Avenue des Martyrs, 38042 Grenoble, France

6. Martin Meven Aachen Institute of Crystallography

   RWTH Aachen University · Forschungszentrum Jülich · Heinz Maier-Leibnitz Zentrum

   Affiliation as printed

   Institute of Crystallography, RWTH Aachen University, 52056 Aachen, Germany

   Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, 85747 Garching, Germany

7. Werner Paulus

   Centre National de la Recherche Scientifique · Université de Montpellier · École Nationale Supérieure de Chimie de Montpellier · Institut Charles Gerhardt Montpellier

   Affiliation as printed

   ICGM, Univ. Montpellier, CNRS, ENSCM, Montpellier 34000, France