AC HOPPING CONDUCTION IN LIGHTLY DOPEDInPAT LOW TEMPERATURES

Abstract

In this paper, AC measurements on lightly doped n-InP were carried out as a function of temperature down to about 16 K and at frequencies in the range from 120 Hz up to 10 5 Hz. The AC conductivity at low temperatures is of a single hopping nature following the universal law; σ(ω) ∼ ω s , where the exponent, s, is temperature-independent. At relatively high temperatures (but still below the room temperature) the AC conductivity is of a multiple hopping nature.

Uncompensated-spins induced weak ferromagnetism in Ca3Mn2O7: Magneto-conductive and dual magneto-capacitive effects

“…Exponent n(T) shown in fig.3(b) encounters down-step, concurrent with the WFM-onset at 110K, with enhanced slope at lower T"s. Evolution of the magnetic state in Ca 3 Mn 2 O 7 , associated with lattice distortion below 110K, affects the energy distribution and hopping distance of charge carriers [31,32]. The higher values of Jonscher exponent observed here, registers significant role of multiple hopping [33,34] (c) Theoretical fit [35] on the dc-resistivity  This is well explained by the clustering theory reflecting electrical conduction occurring via hopping of the charge carriers from "metallic" to insulating regions., given by Sheng et. al.…”

“…3(b) encounters down-step, concurrent with the WFM-onset at 110K, with enhanced slope at lower T"s. Evolution of the magnetic state in Ca 3 Mn 2 O 7 , associated with lattice distortion below 110K, affects the energy distribution and hopping distance of charge carriers [31,32]. The higher values of Jonscher exponent observed here, registers significant role of multiple hopping [33,34]. At appreciably low frequencies, Jonscher power-law fitted  dc follows the resistivity ( dc =1/ dc ) behaviour of the following form, shown in fig.…”

Interplay of spin, lattice, vibration, and charge degrees of freedom: Magneto‐dielectricity in Ca3Mn2O7

“…“Universal law of dielectrics” well describes the total electrical conductivity for the system:Here, ω h defines the hopping frequency at the crossover from dc‐ to ac‐ conduction { σ (ω h ) = 2 σ dc }, which shifts to higher values with increase in temperature. For the correlated electron system in Ca 3 Mn 2 O 7 , multiple hopping mechanism between the charge‐carrier sites explains the ac‐conductivity.…”