Emergence of Ferromagnetism in TbMnO3 Bulk by Al-Doping

Polycrystalline Tb1-xAlxMnO3 (x = 0, 0.05, 0.07, 0.1, 0.2, and 0.3) were synthesized by standard solid-state reaction. The starting precursors Tb4O7, MnO2, Al2O3 were stoichiometric mixed and calcined at 1200 degrees C for 12 hours in air atmosphere. The structural properties of the samples were investigated by X-ray diffraction (XRD) in standard theta-2 theta configuration. The broadening and displacement of the peaks in the XRD diffractograms suggests that the Al doping leads to a distortion of the orthorhombic unit cell of the antiferromagnetic TbMnO3. Careful temperature- and field-dependent magnetic measurements by means of SQUID magnetometry show antiferromagnetic and weak ferromagnetic behavior of the undoped and Al-doped TbMnO3 samples, respectively. Probably, the ferromagnetic response correlates with the unit cell deformation. The results obtained were compared with those achieved in Tb0.7Al0.3MnO3 thin films which were deposited in SrTiO3 and MgO substrates by rf sputtering technique. Due to the close relationship between magnetic order and ferroelectricity in TbMnO3, these results may provide a novel route to induce magnetoelectric coupling and tailor their ferroelectric response.