Search

We have studied some curious effects of an external perturbation on the temperature-dependent field-cooled cool-down magnetization response (MFCC (T)) in a single crystal of a low Tc (≈ 7.10 K) superconductor Ca3Ir4Sn13. The MFCC (T) response in the superconducting state (just below Tc) of this compound shows anomalous paramagnetic magnetization signal(s). In the field-temperature (H-T) region wherein the paramagnetic magnetization occurs in Ca3Ir4Sn13, a perturbation applied to the system in the form of an impulse of an ac magnetic field results in an unpredictable switching of the magnetization from a given paramagnetic value to a diamagnetic or to a different paramagnetic value. The magnetization response is thus found to be multi-valued at a given (H,T) value. The MFCC (T) curves are found to be path-dependent below Tc. Surprisingly, our results obtained in a bulk type-II superconductor Ca3Ir4Sn13 resemble strongly with the characteristics of the magnetization behavior anticipated for the giant vortex states with multiple flux quanta (LΦ0, Φ0 = hc/2e, L > 1) known to occur in the mesoscopic-sized superconductors. [ABSTRACT FROM AUTHOR]

We have studied some curious effects of an external perturbation on the temperature-dependent field-cooled cool-down magnetization response (MFCC (T)) in a single crystal of a low Tc (≈ 7.10 K) superconductor Ca3Ir4Sn13. The MFCC (T) response in the superconducting state (just below Tc) of this compound shows anomalous paramagnetic magnetization signal(s). In the field-temperature (H-T) region wherein the paramagnetic magnetization occurs in Ca3Ir4Sn13, a perturbation applied to the system in the form of an impulse of an ac magnetic field results in an unpredictable switching of the magnetization from a given paramagnetic value to a diamagnetic or to a different paramagnetic value. The magnetization response is thus found to be multi-valued at a given (H,T) value. The MFCC (T) curves are found to be path-dependent below Tc. Surprisingly, our results obtained in a bulk type-II superconductor Ca3Ir4Sn13 resemble strongly with the characteristics of the magnetization behavior anticipated for the giant vortex states with multiple flux quanta (LΦ0, Φ0 = hc/2e, L > 1) known to occur in the mesoscopic-sized superconductors. [ABSTRACT FROM AUTHOR]

We report time differential perturbed angular distribution measurement of 54Fe on a polycrystalline EuFe2As2 sample. The local susceptibility measured shows Curie-Weiss like temperature dependence in the paramagnetic region. The spin-lattice relaxation observed shows Korringa like relaxation and changes discontinuously at TS = TN = 190 K. Below TN, the hyperfine field shows two components. The low filed component of the hyperfine field shows a power law dependence of 0.27 on temperature. [ABSTRACT FROM AUTHOR]

Temperature dependent Raman Spectroscopy study has been performed from 300K to 873K in order to probe the spin-lattice correlation in Rare Earth orthoferrite LaFeO3. The signature of correlation in spin and lattice degrees of freedom is reflected in peak position and/or width around the magnetic ordering temperature in Raman spectra. LaFeO3 has antiferro to paramagnetic transition with Néel temperature of ~740K, which is highest among orthoferrites. The Raman Spectroscopy across magnetic ordering temperature in this compound shows changes in phonon structure as the system transits from antiferromagnetic to paramagnetic region, establishing presence of spin-lattice correlation. [ABSTRACT FROM AUTHOR]

Temperature dependent Raman Spectroscopy study has been performed from 300K to 873K in order to probe the spin-lattice correlation in Rare Earth orthoferrite LaFeO3. The signature of correlation in spin and lattice degrees of freedom is reflected in peak position and/or width around the magnetic ordering temperature in Raman spectra. LaFeO3 has antiferro to paramagnetic transition with Néel temperature of ~740K, which is highest among orthoferrites. The Raman Spectroscopy across magnetic ordering temperature in this compound shows changes in phonon structure as the system transits from antiferromagnetic to paramagnetic region, establishing presence of spin-lattice correlation. [ABSTRACT FROM AUTHOR]

We report magnetization and 111Cd hyperfine field studies in ball milled nanocrystalline CePd3, measured via time differential perturbed angular correlation (TDPAC) spectroscopy. Compared to the Pauli paramagnetic behavior of bulk CePd3, the nanocrystalline samples show enhanced magnetization with field dependence akin to superparamagnetic behavior. This observation is supported by hyperfine field of 111Cd which show temperature dependent large Knightshifts whose magnitude increases with reduction of particle size. [ABSTRACT FROM AUTHOR]

Nanocrystalline Gd2O3 particles of average particle size 25 nm (p25) and 18 nm (p18) are prepared through sol-gel route. Magnetization measurements in both samples show a linear variation of χ-1 with T having two different slopes in the temperature range 30 K- 260 K. In the temperature range 135 K ≤ T ≤ 260 K (TR1) the effective moment (μeff) per Gd3+ is estimated to be 7.70 μB and 7.56 μB whereas, in the temperature range 30 K ≤ T ≤ 135 K (TR2) they are estimated as 7.92 μB and 7.79 μB for p25 and p18, respectively. The enhancement of μeff in the TR2 region may be related with the clustering of spins. Below 30 K, χ-1 deviates from the linearity. At 5K magnetization curve displays superparamagnetic like characteristic features. [ABSTRACT FROM AUTHOR]

The temperature (T) dependent Electron spin resonance (ESR) study was carried out on La0.7-xBixCa0.3MnO3 (x = 0, 0.035, 0.07, and 0.35) samples prepared by sol-gel method. The reduction in the paramagnetic to ferromagnetic (PM-FM) transition temperature (TC) was observed for x = 0.35 sample. ESR studies also reveal the phase separation (PS). The PM phase exists in a wide temperature region even below TC. The ESR linewidth above TC and its temperature dependence is not affected by Bi doping. [ABSTRACT FROM AUTHOR]

Magnetization measurements in the temperature range 4.2 K to 300 K were carried out on [Dy(50Å)/Fe(tFe)]20 multilayers grown by dc magnetron sputtering. From the saturation magnetization, it was inferred that the Dy layers are superparamagnetic due to their nanocrystalline nature. Zero field cooled and field cooled magnetization measurements also confirmed this behaviour. The coercivity of the sample with tFe = 20 Å is much larger than the other samples due to partially ferromagnetic Dy layers. [ABSTRACT FROM AUTHOR]

Magnetic ordering in La-substituted (Bi1-xLax)0.5Pb0.5Fe0.5Ti0.5O3 is investigated for 0.0 ≤ x ≤ 0.5 samples using magnetization measurement as a function of field and temperature. Occurrence of M-H hysteresis loops in all the samples at low temperature suggests existence of magnetically ordered clusters in an overall paramagnetic host. The magnetic ordering temperature is found to increase with increasing x. A decrease in the c/a ratio with x resulting in a reduction of average Fe3+-O-Fe3+ distance along the c direction is argued to enhanced cooperative magnetic interaction of Fe+3-O-Fe+3. [ABSTRACT FROM AUTHOR]

We report time differential perturbed angular distribution measurement of 54Fe on polycrystalline SrFe2As2. The local susceptibility measured shows a Curie-Weiss like temperature dependence in the paramagnetic region. Below TN = 202 K, the hyperfine field shows two components, the low field component showing a power law dependence of 0.25 on temperature. [ABSTRACT FROM AUTHOR]