Adiabatic to non adiabatic change in conduction mechanism of Zn doped La0.67Sr0.33MnO3 perovskite

Abstract

We reported the results of electrical transport properties of La0.67Sr0.33Mn1−xZnxO3 (x=0.1 and 0.2) bulk samples prepared by solid-state reaction route over a wide temperature range from 5 to 300K in the presence of magnetic fields. Powder X-ray diffraction patterns at room temperature confirmed that both samples were formed in a single phase. Temperature dependent resistivity data were fitted using Mott’s variable-range hopping (VRH) model for a limited range of temperatures (from 235.5 to 300K for 10% Zn doped and from 133 to 300K for 20% Zn doped samples) to calculate the hopping distance (Rh) and the density of states near the Fermi level, [N(EF)]. It was found that all the parameters vary systematically with the increase in Zn concentration. Moreover, the temperature dependent resistivity data were also fitted using the small polaron hopping (SPH) model. The adiabatic SPH conduction is followed for 10% doped sample at all fields while a non-adiabatic SPH conduction is found to be active for 20% doped sample in all fields. This type of change in the conduction mechanism is accompanied by subtle electronically induced structural changes involving Mn–O–Mn and Zn–O–Mn bond angles and bond lengths. Thus, we suggest that the transport properties can be explained according to the additional delocalization of charge carriers induced by Zn doping.