Abstract
Single crystals of PrNiO3 were grown under an oxygen pressure of 295 bar using a unique high-pressure optical-image floating zone furnace. The crystals, with volume in excess of 1 mm3, were characterized structurally using single crystal and powder X-ray diffraction. Resistivity, specific heat, and magnetic susceptibility were measured, all of which evidenced an abrupt, first order metal-insulator transition (MIT) at ~130 K, in agreement with previous literature reports on polycrystalline specimens. Temperature-dependent single crystal diffraction was performed to investigate changes through the MIT. Our study demonstrates the opportunity space for high fugacity, reactive environments for single crystal growth specifically of perovskite nickelates but more generally to correlated electron oxides.
Highlights
The nature of the metal-insulator transition (MIT) has been discussed in the literature in terms of charge disproportionation [14,16,31,32,33,34], negative charge transfer [5], and bipolaron condensation [4], but no consensus has been reached
Powder X-ray diffraction data were collected at room temperature on pulverized single crystals using a PANalytical X’Pert Pro powder diffractometer with Cu Kα radiation (Malvern PANalytical, Royston, United Kingdom) (λ = 1.5418 Å) in the 2θ range of 5–80◦
The sample was cooled in zero field to 2 K at a rate of 35 K/min, after which the field was applied, and DC magnetization measurement was performed on warming at 2 K/min (ZFC)
Summary
The transition temperature of the MIT depends on the size of the rare-earth ions, and correlates with the Ni-O-Ni bond angle [1,2,3]. Single crystals of size and quality suitable for neutron diffraction are necessary. It is well-established that high oxygen partial pressure (pO2 ) is needed to prepare polycrystalline specimens of RNiO3 [35,36,37]. We reported the successful single crystal growth of LaNiO3 using a high pressure floating zone furnace [27], and subsequently so did Guo et al [26], reviving interest in this strongly correlated metallic oxide. Electrical resistance and heat capacity measurements on the grown single crystals evidence MITs and show how the MITs and the low-temperature states respond to oxygen stoichiometry
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