Strain-Induced Insulator State and Giant Gauge Factor ofLa0.7Sr0.3CoO3Films

Abstract

A strain-induced change of the electrical conductivity by several orders of magnitude has been observed for ferromagnetic ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{CoO}}_3$ films. Tensile strain is found to drive the narrow-band metal highly insulating. Reversible strain applied using a piezoelectric substrate reveals huge resistance modulations including a giant piezoresistive gauge factor of 7000 at 300 K. Magnetization data recorded for statically and reversibly strained films show moderate changes. This indicates a rather weak strain response of the low-temperature Co spin state. We suggest that a strain-induced static Jahn-Teller–type deformation of the ${\mathrm{CoO}}_6$ units may provide a localization mechanism that also has impact on electronic transport in the paramagnetic regime.