Mn doping instigated multiferroicity and magneto-dielectric coupling in KNbO3

KNb1−xMnxO3 (0 ≤ x ≤ 0.07) samples were synthesized by a two-step process, ball milling of the precursors and then sintering subsequently. Mn doping at Nb site induces a weak ferromagnetism at room temperature and it has been explained with the help of bound magnetic polaron model. Magnetization values at 15 kOe initially increase followed by a decrease with increase in the Mn concentration. Two phase transitions—orthorhombic to tetragonal and tetragonal to cubic, above room temperature were analyzed from the differential scanning calorimetry and temperature dependent dielectric studies. It elucidates the effect of Mn concentration on phase transition temperatures. All the samples exhibit a peak behaviour in the dielectric constant Vs temperature plot at phase transition temperatures. The samples also exhibit leaky ferroelectric loops at room temperature. PUND measurement reveals the true ferroelectric polarization of the samples. The probable origin of magneto-dielectric effect is discussed based on the dielectric study in the presence of variable magnetic field at a frequency of 1 kHz.