arXiv subjects

Aga Shahee

Publications and source records attributed to Aga Shahee.

23 records · Page 2Linked to original sources

arXiv2014

Multiferroic Studies on La0.7Bi0.3CrO3 Perovskite

Magnetic and dielectric properties on a polycrystalline La0.7Bi0.3CrO3 have been investigated. A canted antiferromagnetic (CAF) phase transition giving weak ferromagnetism at TN = 230K has been observed. M-H at 10K shows non-saturating trend, even up to 5T, confirms the CAF ordering. The permittivity (ε')-vs-temperature (T) variation shows a relaxor ferroelectric (RFE) nature accompanied by a pronounced anomaly in ε'-T at TN. The anomaly in ε'-T at TN indicates the presence of magentoelectric (ME) coupling in this material.

cond-mat.str-el↗

arXiv2014

Structural studies on Multiferroic La1-xBixCrO3 Perovskites

The synthesis and structural studies on the polycrystalline La1-xBixCrO3 (x =0, 0.2, 0.25, 0.3, 0.35) have been done using XRD and TEM. The results of the Reitveld refinement of XRD data shows that these compounds crystallize in an orthorhombic structure with Pnma space group. With increasing Bi content, the unit cell volume and lattice parameters undergo non monotonous changes within the tolerance factor from 0.84092 to 0.84072. This has been attributed to the anisotropy induced by lone pair of Bi3+, which may distorted the lattice.

cond-mat.str-el↗

arXiv2014

Oxygen deficiency induced suppression of JT-distortion and stabilization of chargeordering in La0.2Sr0.8MnO3-d

Structural phase transition studies employing low-temperature transmission electron microscopy, and low-temperature x-ray diffraction have been carried out on nearly stoichiometric (δ=0.01) and off-stoichiometric (δ=0.12) versions of La0.2Sr0.8MnO3-δ manganite. The nearly stoichiometric La0.2Sr0.8MnO3-δ under goes a cubic to Jahn-Teller distorted C-type antiferromagnetic tetragonal phase-transition at 260K. For off-stoichiometric La0.2Sr0.8MnO3-δ the Jahn-Teller distorted tetragonal phase transition gets totally suppressed and the basic perovskite lattice remains cubic but shows a charge ordered phase. Stabilization of charge ordered phase in the absence of cooperative Jahn-Teller distortion has been attributed to coulomb-repulsion and Hunds coupling energy. The off-stoichiometric sample shows characteristically different physical properties. This has been realized through transport, magnetic and calorimetric measurements. A smooth crossover from variable range hopping transport to power-law dependence of resistivity (ρ) on temperature (T) i.e. ρ=C.T-α has been realized. This has been attributed to multistep inelastic tunneling through channels involving localized states around oxygen vacancy sites.

cond-mat.str-el↗

arXiv2014

Effect of oxygen off-stoichiometry on coupled structural and magnetic phase-transitions in La0.15Sr0.85MnO3-d (d = 0.02, 0.14)

Effect of oxygen off-stoichiometry on the structural and magnetic properties of La0.15Sr0.85MnO3-d (d = 0.02,0.14) has been studied employing low-temperature x-ray diffraction, calorimetry, electrical-transport and magnetization. The nearly stoichiometric composition under goesfirst order phase-transition from cubic to tetragonal P4/mmm at 238 K accompanied by magnetic and electrical phase-transitions. On the contrary the off-stoichiometric composition does not show any transition and remains cubic Pm-3m down to 80 K. Offstoichiometry induced oxygen-vacancy seems to suppress the cooperative JT distortion and possibly stabilize a G-type antiferromagnetic phase with localized cantedspins. Thus we demonstrate that controlling oxygen stoichiometry is a way of structure/property engineering in electron-doped-like manganites.

cond-mat.mtrl-sci↗

arXiv2011

Glass-like kinetic arrest of first-order structural phase transition in LaxMnO3{\pm}δ (x= 1 & 0.9)

We report here the occurrence of glass-like kinetic-arrest of first-order phase transition of R-3c to Pbnm in a supercooled LaxMnO3\pmδ (X= 1 & 0.9 and δ>0.125) below its insulator-metal transition employing low-temperature transmission electron microscopy (TEM) and x-ray diffraction. No transformation was observed even in a ~12 hrs aged LaxMnO3\pmδ at 98K until unless it was triggered insitu using e-beam irradiation in TEM. A systematic triggering at different temperatures has revealed the occurrence of kinetic-arrest situation similar to stable glass-formers. This has been attributed to the suppression of Johan-Teller distortion by double exchange. PACS number(

cond-mat.str-el↗