Sign inversion of the high-field Hall slope in epitaxialLa0.5Ca0.5MnO3thin films

Abstract

Magnetic and electrical properties of thin epitaxial films of the manganite ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ $(x\ensuremath{\approx}0.5)$ grown by pulsed laser deposition were investigated. The $x=0.5$ composition corresponds to a half-filled ${e}_{g}$ band and is situated on the border between ferromagnetic-metallic and antiferromagnetic-insulating behavior at low temperatures. Both different types of electrical behaviors are observed in samples with similar deposition parameters. This duality may be attributed to phase separation and the occurrence of percolating paths. The insulating ${\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$ samples become metalliclike when magnetic fields of several tesla are applied. Hereby, resistivity drops up to six orders of magnitude occur at 50 K and 12 T. Hall effect measurements on a sample with spontaneous insulator-metal transition show a sign inversion of the high-field Hall slope around 106 K.