Structural, electrical and magnetic properties of magnetoelectric GdMnO3 thin films prepared by a sol-gel method

In this work, we analyzed GdMnO3 magnetoelectric thin films prepared by a general sol-gel method. The film formation temperature is analyzed by a thermogravimetric analysis, while the lattice parameters of the Pbnm orthorhombic films are determined from the analysis of the X-ray spectra. The X-ray results also reveal that GdMnO3 films are under compression along the b axis. The lattice dynamic analysis carried out by a Raman spectroscopy confirms the formation of films with a Pbnm orthorhombic structure. Moreover, the analysis of the Raman spectra suggests that besides film-substrate interaction, texture and grain size influence can alter lattice dynamics relative to the bulk ones. Magnetic measurements show that the film response is different from that observed in ceramic and single crystal; mainly, in the shape and temperature where the transitions are taking place. The magnetic study also reveals that GdMnO3 films are paramagnetic above 80 K, showing a ferromagnetic-like response at low temperatures (T ≤ 15 K). The dielectric analysis carried out on the 850 °C annealed film shows the formation of a relaxation process at low temperature, which is associated with a polaronic process. Moreover, it is also observed a small anomaly at T ~ 27 K that might be related to the magnetic transition taking place in this temperature range.