In-plane Dielectric Properties of Epitaxial Orthorhombic HoMnO3 Films Grown on LaAlO3 Substrates

Orthorhombic HoMnO3 thin films were grown epitaxially on LaAlO3 (001) substrates by using a pulsed laser deposition technique. The films showed perfectly orthorhombic crystallization and were well-aligned with the substrates. The in-plane dielectric constant and the dielectric loss of HoMnO3 films were measured as functions of temperature (80 similar to 300 K) and frequency (120 similar to 100 kHz) by using interdigital surface electrodes. Two thermally-activated dielectric relaxations were found, and the respective peaks shifted to higher temperatures as the measuring frequency was increased. The in-plane dielectric properties of epitaxial orthorhombic HoMnO3 films were considered to have a universal dielectric response behavior, and the dipoar effects and the hopping conductivity induced by the charge carriers were used to explain the results. The dielectric properties at low temperatures, which showed the multiferroicity, of the orthorhombic HoMnO3 films are discussed.