Variation in hopping conduction across the magnetic transition in spinel Mn1.56Co0.96Ni0.48O4 films

Abstract

The temperature dependent dc resistivity of spinel Mn1.56Co0.96Ni0.48O4 (MCN) films is measured in the range of 130–304 K. The hopping exponent p of small polaron hopping conduction shows a clear variation from a value of 0.46 in the paramagnetic to 0.91 in the ferromagnetic phase. In order to explain such variation, a model is proposed where Gaussian distributed localized electron states gradually withdraw from the Hubbard band gap below the magnetic transition as a result of increased magnetic order. This correlation between hopping conduction and magnetic order in MCN films may provide a possible approach to fabricate the devices which couple magnetic and electronic properties in one unit.

High performance of Mn-Co-Ni-O spinel nanofilms sputtered from acetate precursors

“…According to the Nernst–Einstein equation, the temperature dependent resistivity of MCN films is described in the form22:…”

Electrical conduction of intrinsic grain and grain boundary in Mn-Co-Ni-O thin film thermistors: Grain size influence

“…1,5 The electrical conduction of this kind of NTC material is accomplished by the small-polaron hopping between localized Mn 3þ and Mn 4þ (or Co 2þ and Co 3þ ) states under the assistance of thermal activation. 4 The conduction mechanism for these mixedvalence manganites is attractive, but still controversial. The small-polaron hopping models in the non-adiabatic regime for nearest-neighbor-hopping (NNH) or variable-range-hopping (VRH) are mainly discussed.…”

“…[1][2][3][4] It is an important functional material and widely used for temperature compensation devices, temperature sensor devices, surge protection devices, and infrared detecting bolometers. 1,5 The electrical conduction of this kind of NTC material is accomplished by the small-polaron hopping between localized Mn 3þ and Mn 4þ (or Co 2þ and Co 3þ ) states under the assistance of thermal activation.…”

In-plane impedance spectroscopy in aerosol deposited NiMn2O4 negative temperature coefficient thermistor films

“…A temperature dependent activation energy for electron hopping was found many decades ago, 1 but only more recently has a theoretically justified small polaron variable-range hopping (VRH) model been employed more frequently. [32][33][34][35][36] In this work, we present a detailed in-plane impedance spectroscopy (IS) study on approximately 2 lm thick NMO films produced via the aerosol deposition (AD) technique using glass and Al 2 O 3 substrates. 28 The recently developed AD technique offers several distinct advantages: it allows highly dense polycrystalline films of sub-micrometer grain size to be produced with a high deposition rate and without an additional sintering densification process.…”