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

Magnetic properties of carrier controlled YMnO₃ ceramics and undoped epitaxial films were studied. Stoichiometric polycrystalline bulk samples exhibit p-type conduction due to the existence of Mn⁴⁺. The I-V properties are well explained by Poole-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 antiferromagnetic magnetization behavior against the applied magnetic field at 5 K, carrier doped samples displays parasitic ferromagnetic behavior (weak ferromagnetism). Epitaxial films also exhibit antiferromagnetism with little crystallographic anisotropy