Dome-like pressure-temperature phase diagram of the cooperative Jahn–Teller distortion in NaNiO2

DOI: 10.1088/1361-648X/adcb0e

Authors: Liam A. V. Nagle-Cocco (University of Cambridge) , James M. A. Steele (University of Cambridge) , Shiyu Deng (Institut Laue-Langevin) , Xiaotian Zhang (University of Cambridge) , Dominik Daisenberger (Diamond Light Source) , Annalena R. Genreith-Schriever (University of Cambridge) , Siddharth S. Saxena (Cambridge University) , Clare P. Grey (University of Cambridge) , Sian E. Dutton (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Physics: Condensed Matter

State: Published (Approved)
Published: April 2025
Diamond Proposal Number(s): 31718

Abstract: NaNiO$_2$ is a Ni$^{3+}$-containing layered material consisting of alternating triangular networks of Ni and Na cations, separated by octahedrally-coordinated O anions. At ambient pressure, it features a collinear Jahn--Teller distortion below $T^\mathrm{JT}_\mathrm{onset}\approx480$\,K, which disappears in a broad first-order transition on heating to $T^\mathrm{JT}_\mathrm{end}\approx500$\,K, corresponding to the increase in symmetry from monoclinic to rhombohedral. It was previously studied by variable-pressure neutron diffraction [ACS Inorganic Chemistry 61.10 (2022): 4312-4321] and found to exhibit an increasing $T^\mathrm{JT}_\mathrm{onset}$ with pressure up to $\sim$5\,GPa. In this work, powdered NaNiO$_2$ was studied \textit{via} variable-pressure synchrotron x-ray diffraction up to pressures of $\sim$67\,GPa at 294\,K and 403\,K. Suppression of the collinear Jahn--Teller ordering is observed \textit{via} the emergence of a high-symmetry rhombohedral phase, with the onset pressure occurring at $\sim$18\,GPa at both studied temperatures. Further, a discontinuous decrease in unit cell volume is observed on transitioning from the monoclinic to the rhombohedral phase. These results taken together suggest that in the vicinity of the transition, application of pressure causes the Jahn--Teller transition temperature, $T^\mathrm{JT}_\mathrm{onset}$, to decrease rapidly. We conclude that the pressure-temperature phase diagram of the cooperative Jahn--Teller distortion in NaNiO$_2$ is dome-like.

Subject Areas: Physics, Materials


Instruments: I15-Extreme Conditions

Added On: 14/04/2025 08:37

Documents:
Nagle-Cocco+et+al_2025_J._Phys.%3A_Condens._Matter_10.1088_1361-648X_adcb0e.pdf

Discipline Tags:

Physics Hard condensed matter - structures Materials Science

Technical Tags:

Diffraction