Structural correlation to enhanced magnetodielectric properties of Pr-doped polycrystalline Gd$_{0.55}$Pr$_{0.45}$MnO$_3$ at low temperatures

Abstract

The effect of improved dielectric properties in the presence of an applied magnetic field is discussed in Pr doped polycrystalline Gd$_{0.55}$Pr$_{0.45}$MnO$_3$ complemented by the structural properties down to 50 K and magnetic properties. Enhanced dielectric permittivity and low dielectric loss represent the strongly field-dependent dielectric behaviour of the sample. The structural characterizations using synchrotron angle dispersive X-ray diffraction confirm the orthorhombic symmetry of the polycrystalline sample with the Pnma space group from 300 K to 50 K. There is no structural transition at lower temperatures up to 50 K; however the Mn O octahedral distortion is reduced. The investigation of dielectric properties for frequencies range 500 Hz to 1 MHz was conducted in the temperature range 8 K to 300 K with and without a magnetic field of 7 Tesla, which shows the high dielectric constant in the 500 Hz frequency region. This confirms the relaxation phenomena in polycrystalline Gd$_{0.55}$Pr$_{0.45}$MnO$_3$. ac conductivity data shows the increasing trend for frequencies along with the activation energy which increases from low frequencies to higher frequencies. Temperature-dependent dc magnetization study shows the negative magnetization in polycrystalline Gd$_{0.55}$Pr$_{0.45}$MnO$_3$ at low temperature at 100 Oe applied field, due to spin canting of Mn-Mn magnetic lattice. High coercivity due to competition in between spin ordering of Mn and Gd,Pr magnetic lattice at 5 K are also observed in the field-dependent magnetization study.