Magnetic Susceptibility, Electrical Conductivity and Dielectric Constant of Eu_2(WO_4)_3 Single Crystals

概要

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Measurements of magnetic susceptibility (Xm), in all principal crystallographic directions in a temperature range from 4.2 to 900 K, electrical conductivity (σ) and dielectric constant (ε) parallel to the c-axis from 4.2 to 1180 K, of single crystals of Eu_2(WO_4)_3 are reported. The anisotropy observed in Xm is assigned to crystal field effect. It is predicted that, this substance may go in magnetic ordered state below 4.2 K. Electrical conductivity σ has been expalined using polaron concept at high temperatures. It has been shown that, below 790 K, intermediate polarons are the entity of the charge carriers which convert themselves slowly into small polarons in a temperature range of 790 to 900 K. Above 900 K, these small polarons conduct by hopping mechanism assisted by optical phonons. Impurity dominates the conduction below 500 K. Mott's law σ=σ_0(T) exp (-B/T^<1/4>) has been shown to be applicable in a temperature range from 180 to 300 K, with B=2.00(K)^<1/4> and σ_0=6.39×10^<11> ohm^<-1> cm^<-1>. Dielectric constant (ε_0) increases at a slow rate from 4.2 to 500 K. The faster increase in ε_0 above 500 K and discrepancy in the temperature range 790 to 900 K, are assigned to thermally generated polarons and intermediate polaron conversion into small polaron respectively.
社団法人日本物理学会の論文
1976-10-15