Magnetic and Electric Properties of the a-axis-oriented Orthorhombic LuMnO3 Thin Films
We have investigated the structure and magnetic properties of the a-axis-oriented orthorhombic LuMnO3 (o-LuMnO3) films deposited on Nb-doped SrTiO3 (110) substrate by pulsed laser deposition. We observed the anisotropic properties in magnetic structure of o-LuMnO3 by using SQUID (Superconductor Quantum Interference Device) to measure the temperature dependent susceptibility. Two distinctive magnetic transitions were observed for o-LuMnO3 films. The first one locating around 43K was observed universally in each axis and presumably associated with the antiferromagnetic ordering of Mn moment. Consequently, it is assigned as the Neel temperature (TN). The second transition was observed around 30K only when the field was probed along the b-axis, which could be caused by Mn spin reordering. By electric measurement, a transition of the relative permittivity around 30K in a-axis was observed, but the spontaneous polarization was not seen in the electric field dependent polarization curves. It is different from the magnetoelectric correlation predicted by recent theories for these E-type multiferroic manganites. We suspect that the strain effect inherently existing in these epitaxial strain-stabilized orthorhombic films might have played a role.
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