Size effect on multiferroic TbMn2O5 nanorods

Abstract

The effect of the size of TbMn2O5 on their magnetoelectric properties is studied using a field emission transmission electron microscope, ac magnetic susceptibility, relative dielectric constant, specific heat capacity, and x-ray diffraction at various temperatures. A bulk sample and nanorods with two axial lengths, ⟨LC⟩, are investigated. Nanorods with ⟨LC⟩ of 216 nm and 64 nm crystallize with orthorhombic Pbam symmetry as the bulk material. The axial direction of the two sizes of nanorod is parallel to the c axis of the crystal. No particular radial direction is observed. The critical size for the magnetic ordering of TbMn2O5 is found to be between ⟨LC⟩ = 64 nm and 216 nm. Experiments on specific heat capacity verified these results. No similar phenomenon concerning the ferroelectric property is observed. At T = 30 K and 35 K, the ⟨LC⟩ = 216 nm sample yields a charge-ordering-like x-ray diffraction peak, which may be associated with the magnetically induced charge ordering superlattice.