title: Spin phonon interactions and magnetodielectric effects in multiferroic BiFeO3-PbTiO3.
abstract: Here, we report the observation of magneto-dielectric and magneto-structural coupling in (1  -  x)BiFeO3-xPbTiO3 i.e.(1  -  x)BF-xPT) solid solutions with compositions in the vicinity of morphotropic phase boundary, as manifested by a combination of temperature dependent magnetic, Raman and dielectric measurements. Whilst x-ray diffraction and Raman spectroscopy suggest absence of any structural phase transition between 90-300 K, temperature dependent magnetic studies reveal magnetic anomalies in the solid solutions. These results are complemented by identical observations in the dielectric measurements at similar temperatures indicating a coupling between magnetic and electric order parameters. Further, Raman studies on rhombohedral i.e. x  =  0.20 samples reveal a coupling between the magnetic structure and the lattice, causing spin-phonon interactions that are possibly responsible for observed magneto-dielectric effects. Our results illustrate that the phase transitions in BiFeO3-PbTiO3 system are fewer than expected and are attributed to a spatial averaging in an inhomogeneous albeit single-phase material due to clustering of Fe- or Ti-ions on different length scales.
authors.affiliation: Department of Materials Science and Engineering, Indian Institute of Technology Kanpur.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Katoch
authors.forename: C Dhana
authors.initials: CD
authors.lastname: Sekhar
authors.forename: Venimadhav
authors.initials: V
authors.lastname: Adyam
authors.forename: James F
authors.initials: JF
authors.lastname: Scott
authors.forename: Rajeev
authors.initials: R
authors.lastname: Gupta
authors.forename: Ashish
authors.initials: A
authors.lastname: Garg