arXiv subjects

C. Venkateswaran

Publications and source records attributed to C. Venkateswaran.

5 recordsLinked to original sources

arXiv2020

Concurrence of ferroelectric, dielectric and magnetic behaviour in Tb2Ti2O7 pyrochlore

We report the ferroelectric property in Tb2Ti2O7 pyrochlore, prepared by a two-step solid-state reaction method. A concave P-E (polarisation vs electric field) loop observed from 382 K confirms ferroelectricity, below which the loop remains as pointed or banana-shaped. Dielectric plots clearly show an anomaly at 383 K and the magnetic data reveals a deviation from 380 K supporting the observed ferroelectric ordering. The origin of ferroelectricity in Tb2Ti2O7 is discussed which is due to the structural distortion in TiO6 octahedron.

cond-mat.mtrl-sci↗

arXiv2020

First Observed Metal-like to Insulator Transition in the vacant 3d orbital Quantum Spin Liquid Tb$_2$Ti$_2$O$_7$

We report the observation of metal-like to insulator transition (MTI) in the 3dpyrochlore oxide Tb2Ti2O7 at 603 K due to the interaction of empty 3d orbitals of Ti4+ with O2- ions, evidenced by the transition in resistivity. Magnetisation, specific heat capacity and differential scanning calorimetry support the MTI, and the transition is of second order. An appreciable change in magnetisation with temperature, without any magnetic phase transition, is a behaviour typical in this family of compounds which is seldom observed in empty d orbital pyrochlores. The possible mechanism that supports the MTI in Tb2Ti2O7 is discussed. Subsequently, a broad change in magnetisation from 696 K is also seen. Thermogravimetric analysis confirms the observed MTI (603 K) and the broad change in magnetisation (696 K)are not due to oxygen vacancy

cond-mat.mtrl-sci↗

arXiv2019

Crossover to negative dielectric constant in perovskite PrMnO3

Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpiles of unique optical and microwave devices that will also avoid complex geometries. We report the observation of temperature dependent negative dielectric constant (NDC) above 503 K in the perovskite PrMnO3, confirmed through impedance spectroscopy, obeying classical Drude theory. The principle behind the associated negative dielectric loss is explained using the Axelrod mechanism.

cond-mat.mtrl-sci↗

arXiv2018

Magneto-dielectric and Magneto-resistive in the Mixed Spinel MgFe2O4

The mixed spinel, MgFe2O4 has been synthesized by ball-milling assisted sintering method. X-ray diffraction study confirms formation of cubic MgFe2O4 and the lattice parameter values calculated are a = b = c = 8.369(3) Å. Vibrating sample magnetometer measurements at room temperature shows a soft ferrimagnetic nature. Magneto-Dielectric and Magneto-Restive plots confirm coupling at room temperature in the prepared MgFe2O4. The peak at 500 Oe in the MD plot is due to the canting of Fe3+ ions distributed in octahedral and tetrahedral sites.

cond-mat.mtrl-sci↗

arXiv2018

Electrical property of Half Metallic Ferromagnet Pr0.95Mn0.939O3

Half metallic ferromagnetic compounds (HMF) are intensively explored for their potential in spintronics application. According to theoretical studies, HMF are those materials where the conduction mechanism is due to one type of spin state, either up or down. Band theory strongly predicts that Praseodymium (Pr) based transition metal compound (TMC) is HMF whose electrical properties are a consequence of the contribution from both the 4f and 3d orbitals of Pr and TMC ions. Hence, an investigation has been made by preparing Pr0.95Mn0.939O3 by ball milling assisted sintering process. The phase confirmation of the prepared compound is carried out using X-Ray diffraction technique. Impedance analysis with respect to temperature indicates a decreasing trend in electrical conductivity with respect to temperature, confirming the semiconductor behaviour of the sample. This may be due to the consequence of the interaction of 4f and 3d orbitals of the rare-earth (Pr) and transition metal compound (Manganese).

cond-mat.mtrl-sci↗