Janhavi P. Joshi

An electron paramagnetic resonance study of Pr0.6Ca0.4MnO3 across the charge-ordering transition

We report the first electron paramagnetic resonance studies of single crystals and powders of Pr0.6Ca0.4MnO3 in the 300-4.2 K range, covering the charge-ordering transition (Tco) at ~240 K and antiferromagnetic transition (TN) at ~170 K. The asymmetry parameter for the Dysonian single-crystal spectra shows an anomalous increase at Tco. Below Tco the g-value increases continuously, suggesting a gradual strengthening of the orbital ordering. The linewidth undergoes a sudden increase at Tco and continues to increase down to TN. The intensity increases as the temperature is decreased until Tco is reached, due to the renormalization of the magnetic susceptibility arising from the build-up of ferromagnetic correlations.

An electron paramagnetic resonance study of Pr_{0.6}Ca_{0.4}MnO_{3} across the charge ordering transition

We report the first electron paramagnetic resonance studies of single crystals and powders of Pr0.6Ca0.4MnO3 in the 300-4.2 K range, covering the charge-ordering transition (Tco) at ~240 K and antiferromagnetic transition (TN) at ~170 K. The asymmetry parameter for the Dysonian single-crystal spectra shows an anomalous increase at Tco. Below Tco the g-value increases continuously, suggesting a gradual strengthening of the orbital ordering. The linewidth undergoes a sudden increase at Tco and continues to increase down to TN. The intensity increases as the temperature is decreased until Tco is reached, due to the renormalization of the magnetic susceptibility arising from the build-up of ferromagnetic correlations.

Magnetic study of an amorphous conducting polyaniline

We show that newly found BF3-doped polyaniline, although highly conducting, remains amorphous. Magnetic studies reveal many unusual properties, while suggesting that the intrinsic conductivity of this system is significantly larger than all other known forms of conducting polyaniline, establishing it as an interesting class of highly conducting amorphous polymer.

An electron paramagnetic resonance study of electron?hole asymmetry in charge ordered Pr1?xCaxMnO3 (x = 0.64, 0.36)

We present and compare the results of temperature-dependent electron paramagnetic resonance (EPR) studies on

Electron paramagnetic resonance studies of the insulating ferromagnetic manganite Nd0.8Pb0.2MnO3 above the transition temperature

Pr_{1-x}Ca_xMnO_3

Non-resonant microwave absorption evidence for intrinsic Josephson coupling in Tl2Ba2CaCu2O8 single crystals

for x = 0.64, which is electron-doped, with results of studies on the hole-doped, x = 0.36 composition. The temperature dependence of the various parameters obtained from the powder and single crystal spectra showsignificant differences between the two manganites. At room temperature the ‘g’ parameter for the electrondoped system is less than the free electron ‘g’ value ‘ge’, whereas for the hole-doped system it is more than ‘ge’. Further, the linewidth obtained from the powder spectra as well as the single crystal spectra show different functional dependences on temperature in the two systems. Quite strikingly, the peak observed at

Non-resonant microwave absorption studies of superconducting MgB2 and MgB2 + MgO

T_{co}

Temperature-dependent electron paramagnetic resonance studies of charge-ordered Nd0.5Ca0.5MnO3

in the temperature dependence of the asymmetry parameter, \alpha, of the single crystal spectra in the hole-doped system, is absent in the electron-doped system. We understand this contrasting behaviour of the EPR parameters in the two systems in terms of the very different nature of microscopic interactions in them.

On the analysis of broad Dysonian electron paramagnetic resonance spectra

Single crystals of

An electron paramagnetic resonance study of phase segregation in Nd0.5Sr0.5MnO3

Nd_{1-x}Pb_xMnO_3