Room-temperature ferromagnetism and ferroelectricity in nanocrystalline PbTiO3

Nanocrystalline PbTiO3 could exhibit weak room-temperature ferromagnetism (FM). The vacuum annealing enhances FM, while the subsequent air-annealing lowers FM again, indicating that the observed FM is connected with the oxygen vacancies. The reduction of FM with an increase of annealing temperature may be due to the decrease of the amount of oxygen vacancies at the surface of nanograins. The coexistence of ferromagnetism (FM) and ferroelectricity (FE) at room temperature was observed in PbTiO3 pellet with an annealing temperature of 900 °C for 1 h, whereas FE occurs but FM disappears in PbTiO3 pellet with an annealing temperature of 1000 °C for 1 h. The room-temperature magnetodielectric effect was also observed in PbTiO3 multiferroic pellets, indicating the coupling between magnetic and electric properties. The value of ∆ɛr/ɛr(0) for multiferroic PbTiO3 pellet reaches 26.2% at 1 kHz under H = 4.5 kOe.

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