Majhi, Parushottam and Mitra, Saikat and Singh, Akriti and Ghosh, Barnali and Reddy, V R and Saha, Surajit and Raychaudhuri, A K
(2023)
Phase coexistence and resistance relaxation kinetics in NdNiO3 films below the metal-insulator transition temperature.
Physical Review B, 108 (6).
Art No-064103.
ISSN 1098-0121
Abstract
Coexistence of electronically distinct phases below metal-insulator (MI) transition temperature (T-MI) in correlated oxides undergoing temperature-driven MI transition has been observed in a number of systems. One of the consequences of the coexisting phases is that the metastable high-temperature metallic phase transforms into the stable insulating phase with a finite relaxation time as the temperature is lowered below T-MI. We report an extensive investigation of the phase transformation (referred to as relaxation) using resistivity as a tool where the ramp-dependent hysteresis and isothermal annealing-induced resistance relaxation were studied in films of NdNiO3 grown on three different crystalline substrates (LaAlO3, SrTiO3, and BaTiO3/SrTiO3) down to 10 K, well below the metal-insulator transition temperature. The resistance relaxation experiments were complemented with Raman spectroscopy and high-resolution x-ray diffraction done down to 5 K and reciprocal space mapping (RSM). Isothermal annealing experiment done to temperatures < T-MI shows that the average relaxation time (tau) decreases on cooling. This can arise from a temperature-dependent barrier to relaxation, where the barrier reduces continuously on cooling down to a temperature, referred to as T*. T* has been interpreted as a likely limit of supercooling so that the relaxation time -> 0 at this temperature. The resistance relaxation data were linked to x-ray diffraction and Raman spectroscopy data done to temperatures well below T-MI, in order to have a structural basis for the coexisting phases and their likely participation in the relaxation process. The experiments (both hysteresis and isothermal annealing) were analyzed by Monte Carlo simulation based on a minimal set of parameters, namely, a temperature T* and an energy scale of transformation E*, which themselves had a temperature dependence. The parameters used in the simulation and other experimentally observed quantities like the width and height of hysteresis were found to be correlated with certain structural parameters, in particular, the residual in-plane strain and the crystallite grain size that determine the size range in these films.
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