D Bhoi

Giant magnetocaloric effect in magnetically frustrated EuHo2O4 and EuDy2O4 compounds

We have investigated the magnetic and magnetocaloric properties of EuHo2O4 and EuDy2O4 by magnetization and heat capacity measurements down to 2 K. These compounds undergo a field-induced antiferromagnetic to ferromagnetic transition and exhibit a huge entropy change. For a field change of 0-8 T, the maximum magnetic entropy and adiabatic temperature changes are 30 (25) J kg−1 K−1 and 12.7 (16) K, respectively, and the corresponding value of refrigerant capacity is 540 (415) J kg−1 for EuHo2O4 (EuDy2O4). These magnetocaloric parameters also remain large down to lowest temperature measured and are even larger than that for some of the potential magnetic refrigerants reported in the same temperature range. Moreover, these materials are highly insulating and exhibit no thermal and field hysteresis, fulfilling the necessary conditions for a good magnetic refrigerant in the low-temperature region.

Resistivity saturation in PrFeAsO1−xFy superconductor: evidence of strong electron–phonon coupling

We have measured the resistivity of PrFeAsO1−xFy samples over a wide range of temperature in order to elucidate the role of electron–phonon interaction on normal- and superconducting-state properties. The linear T dependence of ρ above 170 K followed by a saturation-like behavior at higher temperature is a clear signature of strong electron–phonon coupling. From the analysis of the T dependence of ρ, we have estimated several normal-state parameters that are useful for understanding the origin of superconductivity in this system. Our results suggest that Fe-based oxypnictides are phonon-mediated BCS superconductors like Chevrel phases and A15 compounds.

3d-4f spin interaction induced giant magnetocaloric effect in zircon-type DyCrO4 and HoCrO4 compounds

We have investigated the influence of 3d-4f spin interaction on magnetic and magnetocaloric properties of DyCrO4 and HoCrO4 compounds by magnetization and heat capacity measurements. Both the compounds exhibit complicated magnetic properties and huge magnetic entropy change around the ferromagnetic transition due to the strong competition between ferromagnetic and antiferromagnetic superexchange interactions. For a field change of 8 T, the maximum values of magnetic entropy change (ΔSMmax), adiabatic temperature change (ΔTad), and refrigerant capacity (RC) reach 29 J kg−1 K−1, 8 K, and 583 J kg−1, respectively, for DyCrO4 whereas the corresponding values for HoCrO4 are 31 J kg−1 K−1, 12 K, and 622 J kg−1. ΔSMmax, ΔTad, and RC are also quite large for a moderate field change. The large values of magnetocaloric parameters suggest that the zircon-type DyCrO4 and HoCrO4 could be the potential magnetic refrigerant materials for liquefaction of hydrogen.

Quantum magnetoresistance of the PrFeAsO oxypnictide

We report the observation of an unusual

3d-4f spin interaction and field-induced metamagnetism in RCrO4 (R = Ho, Gd, Lu) compounds

B

Vortex dynamics and second magnetization peak in PrFeAsO0.60F0.12 superconductor

dependence of transverse magnetoresistance (MR) in the PrFeAsO, one of the parent compound of pnictide superconductors. Below the spin density wave transition, MR is large, positive and increases with decreasing temperature. At low temperatures, MR increases linearly with

Normal-state transport properties of PrFeAsO1−xFy superconductor

B

Effect of pressure on the magnetic and superconducting transitions of GdFe1−xCoxAsO (x = 0, 0.1, 1) compounds

up to 14 T. For

Effect of pressure on normal and superconducting state properties of iron based superconductor PrFeAsO0.6F y (y = 0.12, 0.14)

T