Magnetic phase characterization of nanocrystalline La2NiMnO6 using alternating current conductance

Abstract

The signature of various disordered phases is inferred from the measurement of the real part of alternating current conductance Σ(T, f) of a nanocrystalline double perovskite La2NiMnO6. The system exhibits a paramagnetic insulating (PMI) phase at high temperatures, a ferromagnetic insulating (FMI) phase at low temperatures, and a Griffiths-like phase in the intermediate temperature range. In these three phases, Σ(T, f) shows qualitatively similar variation with frequency f. At a fixed temperature T, Σ(T, f) remains constant to its Ohmic value Σ0 up to a certain frequency, known as the onset frequency fc and increases with increasing f beyond fc. Scaled appropriately, Σ(T, f) versus f data corresponding to these three regimes fall on the same master curve indicating the universal nature of the scaling behaviour of alternating current conductance. This onset frequency fc scales with Σ0 as fc∼Σ0xf with xf as the nonlinearity exponent. This exponent xf shows a gradual crossover from 1.025 ± 0.006 in FMI phase to 0.518 ± 0.07 in PMI phase in an intermediate temperature range signifying the presence of Griffiths-like phase. A simple phenomenological R–RC model consistent with the microstructural conduction mechanisms in PMI and FMI phases is developed to generate the qualitative non-Ohmic character of ac conductance, the onset frequency fc, and the nonlinearity exponent xf. Existing scaling theories with reliable models are used to analyze and compare the results of ac conductance in similar systems.

Effect of Annealing Temperature on the Structural and the Electrical Transport Properties of La2NiMnO6 Nanoparticles

“…Such decrease of ASD introduces more homogeneity in the sample with a reduction of unfavorable sites for conduction. Moreover it can be stated that the increase in homogeneity in the samples increases the corresponding grain sizes which leads to smaller number of grain boundaries . This in turn increases the value of Ohmic conductance .…”

Effect of anti-site disorder on magnetism in La2NiMnO6

“…La 2 NiMnO 6 is a ferromagnetic insulating double-perovskite, that has been widely investigated over the last decade [1][2][3][4][5][6][7][8][9][10][11] . La 2 NiMnO 6 can form in two distinct crystallographic forms, a monoclinic P2 1 /n structure or in a rhombohedral R3 structure.…”

Possibility of controlling the conduction mechanism by choosing a specific doping element in a praseodymium manganite system

“…8 (a-d existence of general formalism for the AC conductance in perovskite materials. 63,64 For Co-PCMO compound, the obtained result conrms the existence of two dissimilar variations. Below n/n H z 2, the spectra are perfectly collapsed to a single master curve.…”

“…To get an idea about the charge transport properties and with a view to examine the validity of the time temperature superposition principle, we interest on the application of scaling model. [63][64][65] In such approach, the frequency and the conductance axis must be scaled with respect to the hooping frequency (n H ) and the DC conductance (G dc ) parameters, respectively. The curves of the conductance spectra are scaled using the following relation: Fig.…”