Effect of carrier concentration on the magnetic behavior of ferroelectric YMnO3 ceramics and thin films.

Magnetic Properties of carrier controlled YMnO3 ceramics and un-doped epitaxial films were studied. Stoicheometric polycrystalline bulk sample exhibit p-type conduction due to the existence of Mn4+. The I-V property is well explained the Pool-Frenkel type carrier emission, and the activation energy is calculated to be 0.38 eV. The carrier density decreases by Zr doping and increases by Li or Mg doping. Although all the samples exhibit anti-ferromagnetic magnetization behavior against the applied magnetic field at 5 K, carrier doped samples displays parasitic ferromagnetic behavior (weak ferromagnetism). Epitaxial film also exhibit anti-ferromagnetism with little crystallographic anisotropy.