Articles written in Pramana – Journal of Physics
Volume 58 Issue 5-6 May 2002 pp 713-714
Volume 58 Issue 5-6 May 2002 pp 949-954 Physics Of Vortex State
The vortex dynamics at microwave frequencies in YBa2Cu3O7-δ (YBCO) films have been studied. We observe a peak in the microwave (4.88 and 9.55 GHz) surface resistance in some films in magnetic fields up to 0.8 T. This is associated with the ‘peak-effect’ phenomenon and reflects the order-disorder transformation of the flux line lattice near the transition temperature. Introduction of artificial pinning centers like columnar defects created as a result of irradiation with 200 MeV Ag ion (at a fluence of 4×1010 ions/cm2) leads to the suppression of the peak in films previously exhibiting ‘peak effect’.
Volume 58 Issue 5-6 May 2002 pp 955-958 Physics Of Vortex State
A pronounced peak in the microwave (at frequency 9.55 GHz) surface resistance,
Volume 58 Issue 5-6 May 2002 pp 959-963 Physics Of Vortex State
We report the observation of a propounced peak in surface resistance at microwave frequencies of 4.88 GHz and 9.55 GHz and its disappearance after irradiation with swift ions in laser ablated DyBa2Cu3O7-δ (DBCO) thin films. The measurements were carried out in zero field as well as in the presence of magnetic fields (up to 0.8 T). The films were irradiated using 90 MeV oxygen ions at Nuclear Science Centre, New Delhi at a fluence of 3×1013 ions/cm2. Introduction of point defects and extended defects after irradiation suppresses the peak at 9.55 GHz whereas no suppression is observed at 4.88 GHz. These results and the vortex dynamics in the films at microwave frequencies before and after irradiation are discussed.
Volume 58 Issue 5-6 May 2002 pp 1003-1008 Colossal Magnetoresistance And Other Materials
In this paper we report synthesis of phase-pure highly resistive magnetoelectric BiFeO3 thin films on Pt/TiO2/SiO2/Si substrate by using pulsed laser deposition technique. For the first time saturated ferroelectric hysteresis loop has been observed. It has confirmed the presence of ferroelectricity in BiFeO3 compound. The films exhibit dielectric anomaly near Neel temperature. This anomaly is related to the influence of vanishing magnetic order on the electric order.
Volume 58 Issue 5-6 May 2002 pp 1027-1030 Colossal Magnetoresistance And Other Materials
In this paper, we report for the first time finite size effects on Néel temperature (
Volume 58 Issue 5-6 May 2002 pp 1041-1044 Colossal Magnetoresistance And Other Materials
Electrical resistance (
Volume 58 Issue 5-6 May 2002 pp 1089-1092 Colossal Magnetoresistance And Other Materials
Epitaxial La0.2Nd0.4Ca0.4MnO3 thin films have been deposited at 800°C on LaAlO3 substrate using pulsed laser deposition technique. The structural and magnetotransport properties of the films have been studied. The sharp peak in the temperature dependence of the resistance corresponding to metal-to-insulator transition (
Volume 58 Issue 5-6 May 2002 pp 1147-1151 Thin Film And Devices
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed
Volume 58 Issue 5-6 May 2002 pp 1165-1170 Thin Film And Devices
La0.67Ba0.33MnO3 (LBMO) thin film is deposited on a 36.7°C SrTiO3 bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears at temperature
Volume 58 Issue 5-6 May 2002 pp 1171-1177 Thin Film And Devices
Microwave surface resistance (
Volume 58 Issue 5-6 May 2002 pp 1179-1182 Thin Film And Devices
Hole-doped rare-earth manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 both show a metal-insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal-insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La0.7Ce0.3MnO3 could be a minority spin carrier ferromagnet. The implication of this observation is discussed.
Volume 58 Issue 5-6 May 2002 pp 1199-1201 Thin Film And Devices
We report here injection of spin-polarized carriers from a half-metallic La0.3Ca0.7MnO3 (LCMO) colossal magnetoresistive (CMR) thin film into a high-temperature superconducting YBa2Cu3O7-δ (YBCO) thin film studied using a micro-bridge. The LCMO and YBCO films were grown on 〈100〉 LaAlO3 (LAO) substrate sequentially using pulsed laser deposition (PLD).