Vijaylakshmi Dayal

Evolution of Griffith's phase in La0.4Bi0.6Mn1−xTixO3 perovskite oxide

Samples of La0.4Bi0.6Mn1−xTixO3 have been prepared and their microstructure, composition, and magnetic properties have been investigated for x = 0.05, 0.1, and 0.5.The deviation in the inverse susceptibility behavior from Curie-Weiss law and increase in susceptibility exponent indicates the evolution of the Griffiths phase in La0.4Bi0.6Mn1−xTixO3 around TC. The presence of Griffiths Phase is inferred due to magnetic frustration with increasing Ti concentration. The deviation between field cooled and zero field cooled magnetization curves is observed in these samples and is attributed to the appearance of the spin glass or cluster glass state that arises due to the magnetic anisotropy.

Magnetic Interaction and Electronic Transport in La 0.4 Bi 0.6 Mn 0.5 Ti 0.5 O 3 Manganite

We report magnetic interactions and electronic transport properties in La0.4Bi0.6Mn0.5Ti0.5O3 perovskite manganite synthesized using solid-state route. After characterizing the samples structurally, the systematic investigations of magnetic and electrical transport behaviors have been undertaken. It has been observed that at low temperatures near TC , the sample is magnetically frustrated leading to the second-order magnetic transition. A justification for the observed magnetic behavior has been explained based on Arrott’s plot study. The resistivity as a function of temperature in the absence and the presence of applied magnetic field suggests semiconducting nature of the sample. The conduction of the charge carriers is explained using Shklovskii-Efros-type variable-range-hopping mechanism.

Investigation of phase coexistence and correlation in La1−xBixMnO3+δ (x = 0.4 and 0.6)

Polycrystalline samples of bismuth-doped (x?=?0.4 and 0.6) have been synthesized using conventional solid state reaction methods. After characterizing the samples by x-ray diffraction, scanning electron microscope, and energy dispersive x-ray spectrometer, a systematic investigation of magnetic, electrical, and magneto-transport properties has been carried out. Our magnetic measurements indicate spin-glass magnetic behaviour accompanied by a ferromagnetic phase at low temperatures. Also, the evidence for phase coexistence, leading to overlapping of the nanoscale ferromagnetic phase in the paramagnetic host matrix is observed. The electrical resistivity measurements suggest the semiconducting nature of the samples in the measured temperature range. For both samples, the conductivity in the temperature range above the (for T?>??D/2) is observed to be due to the adiabatic hopping of small polarons, whereas below the (for T?<??D/2), the Shklovskii?Efros variable range hopping mechanism appears to be suitable. The dielectric permittivity as a function of temperatures and frequencies studied in the samples exhibits different relaxation processes, which are understood due to the Debye+Maxwell?Wagner relaxation mechanisms. The observed negative magneto-resistivity and the dielectric relaxation in the paramagnetic region can be attributed to the phase coexistence scenario.

Critical behavior and non-universal low-field magnetic scaling in La1-xBixMnO3 (x=0.4 & 0.6) perovskite manganite oxide

We report on critical behavior in La1-xBixMnO3 (x=0.4 & 0.6) perovskite manganite oxide by studying AC susceptibility, χ, measured at randomly chosen low magnetic fields (H=9.45 Oe to 0.95 Oe) at fixed frequency of f=131 Hz. The samples exhibit non-uniformity in their magnetic spin interactions around paramagnetic-to-ferromagnetic transition temperature (TC). By non-universal low-field magnetic scaling of AC χ given as, χ−1-χ−1(TC) ∼ (T/TC−1)γ ≡ τγ the magnetic interactions in the samples around TC has been studied. The linear fit to ln (χ−1 - χC−1) vs. ln (T/TC-1) gives the values of critical exponent ‘γ’ under applied magnetic fields. The values of γ is found to be ∼1.48±0.007 for the sample with x=0.4 and ∼1.36±0.004 for x=0.6 at 0.95 Oe lie in the context of 3D Heisenberg type spin interactions. The profound 3D Heisenberg type spin interactions arises due to the phase separation effect for x=0.4 and breaking of ferromagnetic order and induced Bi3+ (6S2) − O2− (2P6) lattice distortions for x=0.6 as dis...

Investigation of magnetic spin glass property in La0.5Bi0.5MnO3 sample using non-linear AC susceptibility measurements

We present a comprehensive study on origin of Spin Glass (SG) property in polycrystalline La0.5Bi0.5MnO3 perovskite oxide using linear and higher order ac susceptibility (χ) measurements. The third order harmonic susceptibility (χ3) vs. temperature (K) with varying magnetic fields from 0.95 to 9.45 Oe and the divergence in their χ3 (max) allows us to infer the SG behavior occurring in the sample possibly due to co-operative freezing of the spins.

Electrical and magnetic properties of La0.5Bi0.5MnO3

The sample La0.5Bi0.5MnO3 has been prepared using conventional solid state route method. Electrical properties of the sample have been understood with effective use of various models like thermally activated conduction (TAC), Variable Range Hopping (VRH) and Spin polarized Hopping (SPH). The temperature dependence of the zero field cooled (ZFC) and field cooled (FC) magnetization at a field of 100(Oe) supports the compound has a trend of spin or cluster glass phenomenon. The temperature dependent magnetic phase has been studied in detail to understand the nature of ferromagnetic (FM) interactions. The distinct phase separated FM and AFM clusters with due competition between them giving rise to glassy state in the system has been understood.