Continuous transition from weakly localized regime to strong localization regime in Nd0.7La0.3NiO3 films

Bisht, Ravindra Singh and Daptary, Gopi Nath and Bid, Aveek and Raychaudhuri, A. K. (2019) Continuous transition from weakly localized regime to strong localization regime in Nd0.7La0.3NiO3 films. In: JOURNAL OF PHYSICS-CONDENSED MATTER, 31 (14).

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Abstract

We report an investigation of metal-insulator transition (MIT) using conductivity and magnetoconductance (MC) measurements down to 0.3 K in Nd0.7La0.3NiO3 films grown on crystalline substrates of LaAlO3 (LAO), SrTiO3 (STO), and NdGaO3 (NGO) by pulsed laser deposition. The film grown on LAO experiences a compressive strain and shows metallic behavior with the onset of a weak resistivity upturn below 2 K which is linked to the onset of weak localization contribution. Films grown on STO and NGO show a cross-over from a positive temperature coefficient (PTC) resistance regime to negative temperature coefficient (NTC) resistance regime at definite temperatures. We establish that a cross-over from PTC to NTC on cooling does not necessarily constitute a MIT because the extrapolated conductivity at zero temperature (lim(T -> 0) sigma - sigma(0)) though small (< 10 S cm(-1)) is finite, signaling the existence of a bad metallic state and absence of an activated transport. The value of sigma(0) for films grown on NGO is reduced by a factor of 40 compared to that for films grown on STO. We show that a combination of certain physical factors makes substituted nickelate (that are known to exhibit first-order Mott type transition), undergo a continuous transition as seen in systems undergoing disorder/composition driven Anderson transition. The MC measurement also supports the above observation and shows that at low temperatures, there exists a positive MC that arises from the quantum interference which co-exists with a spin-related negative MC that becomes progressively stronger as the electrons approach a strongly localized state in the film grown on NGO.

Item Type:	Journal Article
Publication:	JOURNAL OF PHYSICS-CONDENSED MATTER
Publisher:	IOP PUBLISHING LTD
Additional Information:	Copyright of this article belongs to IOP PUBLISHING LTD
Keywords:	continuous transition; disorder; strain; fermi/non-fermi liquid; bad metal
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	17 May 2019 09:46
Last Modified:	17 May 2019 09:46
URI:	http://eprints.iisc.ac.in/id/eprint/62394

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