Electrical transport properties ofLaNi1−xMxO3 (M = Co,Mn) thin films fabricated by pulsed laser deposition

Abstract

Highly oriented thin films of LaNi1−xMxO3 (M = Mn, Co) aregrown on LaAlO3(100) substrate by pulsed laser deposition. They undergo a metal to insulator transition when theMn or Co concentration is increased. The observed conduction pattern is highly sensitive tothe doping concentration in these thin films. The conduction pattern also varies as the dopingelement is varied from Mn to Co. There is a large dominance of electron–lattice interactionsin the conduction mechanism of the charge carriers. While the metallic thin films ofLaNi1−xCoxO3 show a linear variation of resistivity with temperature,LaNi1−xMnxO3 thin films exhibit a prominent square-root dependence of resistivity on temperature. At highconcentrations of Mn or Co, the conduction takes place via a polaron hopping mechanism,which suggests that lattice polarization may be present in these films. The change observedin the transport properties is attributed to the charge disproportionation between theNi3+–Ni2+ pairs, which are favoured more in Mn doped thin films. The photoelectron spectroscopicstudies give evidence of charge disproportionation present in these films.