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High-pressure study of the elpasolite perovskite La2NiMnO6

DOI: 10.1021/acs.inorgchem.9b00404 DOI Help

Authors: Christopher J. Ridley (ISIS Neutron and Muon Source) , Dominik Daisenberger (Diamond Light Source) , Craig W. Wilson (Diamond Light Source) , Gavin B. G. Stenning (ISIS Neutron and Muon Source) , Gopinathan Sankar (University College London) , Kevin S. Knight (University College London; The Natural History Museum) , Matthew Tucker (ISIS Neutron and Muon Source) , Ronald I. Smith (ISIS Neutron and Muon Source) , Craig L. Bull (ISIS Neutron and Muon Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Inorganic Chemistry

State: Published (Approved)
Published: June 2019
Diamond Proposal Number(s): 11828

Abstract: Here we report a high-pressure investigation into the structural and magnetic properties of the double perovskite La2NiMnO6 using neutron scattering over a temperature range of 4.2–300 K at ambient pressure and over a temperature range of 120–1177 K up to a maximum pressure of 6.6 GPa. X-ray diffraction was also used up to a maximum pressure of 64 GPa, over a temperature range of 300–720 K. The sample was found to exist in a mixed rhombohedral/monoclinic symmetry at ambient conditions, the balance of which was found to be strongly temperature- and pressure-dependent. Alternating current magnetometry and X-ray absorption near-edge structure measurements were made at ambient pressure to characterize the sample, suggesting that the transition-metal sites exist in a mixed Ni3+/Mn3+ and Ni2+/Mn4+ state at ambient temperature and pressure. Analysis of the magnetic properties of the sample shows that the Curie temperature can be enhanced by ∼12 K with 2 GPa applied pressure, but it is highly stable at pressures beyond this. We report a pressure–volume–temperature equation of state for this material over this combined temperature and pressure range, with an ambient temperature bulk modulus of ∼179(8) GPa. The previously reported transition from monoclinic to rhombohedral symmetry upon heating to 700 K is seen to be encouraged with applied pressure, transforming fully by ∼1.5 GPa. Raman spectroscopy data were collected up to ∼8 GPa and show no clear changes or discontinuities over the reported phase transition to rhombohedral symmetry or any indication of further changes over the range considered. The ambient-pressure Grüneisen parameter γth was determined to be γth = 2.6 with a Debye temperature of 677 K. The individual modal parameters γj at ambient temperature were also determined from the high-pressure Raman data.

Subject Areas: Materials, Chemistry, Physics


Instruments: I15-Extreme Conditions