Anisotropic electrical and magnetic properties of epitaxial Ga$_{2-x}$Fe$_{x}$O$_{3}$ thin films with different crystalline orientations

Anisotropy of electrical and magnetic properties in magnetoelectric and multiferroic materials is an important issue for applications of the materials to electronic devices. Ga$_{2-x}$Fe$_{x}$O$_{3}$ (GFO) has been known as a pyroelectric ferrimagnet at room temperature when x $>$ 1.4. GFO exhibits a permanent polarization along $b$-axis while a spontaneous net magnetization along $c$-axis. Exploration of its anisotropic properties requires preferentially oriented epitaxial thin films of GFO with different crystalline orientations. We have grown successfully $b$-axis oriented GFO thin films on indium-tin oxide(001)/yttria-stabilized zirconia(001). Two additional bottom electrodes such as SrRuO$_{3}$ on SrTiO$_{3}$(111), (110) and (100) and Pt(111)/Ti/SiO$_{2}$/Si substrates were used for epitaxial growth of GFO. X-ray diffraction and transmission electron microscopy have been performed. Dielectric permittivity of the GFO films was measured with external magnetic field as a function of temperature. Local polarization switching behavior was characterized by scanning probe microscopy, which can give a clue to answer a debating question that GFO thin films are pyroelectric with no bistable switching states.