Novel Near-Room-Temperature Type I Multiferroic: Pb(Fe_0.5Ti_0.25W_0.25)O₃ with Coexistence of Ferroelectricity and Weak Ferromagnetism

We report on the crystal structure evolution and the physical properties of the complex perovskite Pb­(Fe_0.5Ti_0.25W_0.25)­O₃. It presents a paraelectric to ferroelectric transition at <i>T</i>_C = 293 K, determined by permittivity measurements. The room-temperature neutron powder diffraction pattern (NPD) shows an admixture of the ferroelectric phase (34%, <i>P</i>4<i>mm</i> space group) and the paraelectric polymorph (66%, <i>Pm</i>3̅<i>m</i> space group). In both polymorphs, the perovskite crystal structure contains the three B cations (Fe, Ti, W) distributed at random at the octahedral sites, and Pb is shifted away from the center of the cubic (sub)­cell. On the other hand, the presence of iron drives the appearance of magnetic interactions above room temperature. This is related to the existence of Fe-rich islands where the strong Fe³⁺–O–Fe³⁺ superexchange interactions govern the magnetic behavior. The magnetic structure has been determined from low-temperature NPD experiments as a G-type antiferromagnetic (AFM) cell. Furthermore, there is a net magnetization in the entire range of temperature, which is related to the existence of noncompensated spins in each island. The coexistence of ferroelectricity and a magnetically ordered state and the observation of a possible coupling between both phenomena allow us to suggest the multiferroic-magnetoelectric nature of the sample