Magnetic properties and potential barrier between crystallites model of MgGa2-xFexO4 ceramics

Abstract

The aim of this work was to investigate the magnetic properties and the electrical conductivity temperature dependence associated to the potential barrier between the crystallites model. Gallium and magnesium containing spinel ceramic has low magnetic coercivity and high electrical resistivity. MgGa2-xFexO4 samples (x= 0.01, 0.05, 0.15, 0.25, 0.35) were prepared by solid-state method and sintered at 800 °C for 8 h. X-ray diffraction analysis confirmed the formation of a single phase with compact cubic spinel structure. The magnetic measurements show that the saturation magnetization and remanence of all samples increased with increasing iron concentration. The coercive field decreased up to the concentration x= 0.15, and above x= 0.25 it was observed an increase in the coercive field. Through electrical characterization it was found that the samples presented highly insulating behavior for x= 0.01, and further increase in x above 0.15 gives a semiconductor behavior compatible with the potential barrier between the crystallites model, i.e. fulfills the condition L/2 > LD (crystallite size L in comparison with the Debye length LD), and the conduction is limited by potential barriers between the crystallites.

Caracterização Elétrica E Estrutural Da Cerâmica De Chumbo E Cobre

“…This model states that, when the trapping states in grain region are unoccupied, they create a depletion region in the grain and a potential barrier at the interface. This reduces the number of free carriers available for electrical conduction [14]. The electrical transport in all of the investigated samples is related to charged impurities carrier scattering mechanism in the region between the grains [20].…”

“…The dielectric permittivity of all samples have been calculated considering a.c. capacitance measurements in the frequency range of 1 Hz to 10 MHz and Equation 4. In this equation, is the capacitance of the pellet, d is the thickness of the pellet, A is the cross-sectional area of the flat surface of the pellet [14,16,17].…”

“…The applicability of this model is tested by the Debye-length (L D ) given by Equation 3, i.e. if L D < L/2, the activation energy is due to carrier trapping by ionized deep level defects at the crystallite boundaries [14,15]. sites occupied by cations.…”