Effect of particle size and annealing on spin and phonon behavior in TbMnO3

Abstract

Interest has grown to study TbMnO3 as it was recently reported to show a gigantic magnetoelectric effect. Here, we report the synthesis and detailed magnetic and Raman spectroscopy study on TbMnO3 particles of size ∼25 nm and μ2-3 m, respectively. The incommensurate-commensurate (lock-in) transition, usually observed at 27 K for bulk phase of TbMnO 3 was not observed in susceptibility versus T curve but was seen at 30 K in the coercivity versus T curve in ∼25 nm particles. This transition, which is due to the spin modulation length scale, gets weakened in nanosize due to the increased intrinsic lattice strain observed in 2-3 μm particles, due to the effect of increased particle size. The increased value of magnetization in the 2-3 μm sample was attributed to double exchange interactions between Mn3 and Mn4 spins. The role of annealing related effects on the fate of the Néel temperature for TbMnO3 was investigated. Raman spectroscopy indicated a decrease in the lattice distortion for ∼25 nm particles. © 2011 American Institute of Physics.