Reentrant metallic transition at a temperature above Tc at the breakdown of cooperative Jahn-Teller orbital order in perovskite manganites

TL;DR

This study reveals a reentrant metallic transition at temperatures above typical magnetic and orbital ordering points in certain perovskite manganites, challenging existing understanding of their phase behavior.

Contribution

It reports an unexpected reentrant metallic transition above characteristic temperatures in La(1-x)Ca(x)MnO(3), contrary to the usual behavior observed in doped manganites.

Findings

Reentrant metallic resistivity pattern observed above T*

Behavior occurs in systems without prior orbital order breakdown

Challenges existing phase transition models in manganites

Abstract

We report an interesting reentrant metallic resistivity pattern beyond a characteristic temperature T* which is higher than other such characteristic transition temperatures like T(c)(Curie point), T(N) (Neel point), T(CO) (charge order onset point) or T(OO) (orbital order onset point) in a range of rare-erath perovskite manganites (RE(1-x)A(x)MnO(3); RE = La, Nd, Y; A = Sr, Ca; x = 0.0-0.5). Such a behavior is normally observed in doped manganites with doping level (x) higher than the critical doping level x(c) (= 0.17-0.22) required for the metallic ground state to emerge and hence in a system where cooperative Jahn-Teller orbital order has already undergone a breakdown. However, the observation made in the La(1-x)Ca(x)MnO(3) (x = 0.0-0.5) series turns out to be an exception to this general trend.