Thin films of semiconducting lithium ferrite produced by pulsed laser deposition

Abstract

Thin films of lithium ferrite (Li0.5Fe2.5O4) have been deposited on (0 0 1) Al2O3 by pulsed laser deposition, with substrate deposition temperatures ranging between 500 and 800 °C, and oxygen pressures between 1 × 10−1 and 4 × 10−7 mbar. X-ray diffraction shows that films grow with a (1 1 1) orientation. Conversion electron Mössbauer spectra for the high-pressure films show a single sextet with a hyperfine field of 49 T, while the low-pressure films show two sextets with hyperfine fields of 47 and 49 T. The spectra also reveal paramagnetic ferric iron in both types of films. Magnetization measurements of the films show a saturation magnetization of between 1.7 and 3.1μB per formula unit and a coercivity of between 10 and 44 mT. The films prepared under the lower oxygen pressures are semiconducting with resistivities of 2 × 10−2 to 8 × 10−2 Ω cm. They exhibit an anomalous Hall effect with p-type conduction at 175 K.