As Lagutin

A probe for magnetization measurements of thin superconducting films in pulsed high magnetic fields

This paper describes an inductive magnetization sensor, designed to measure thin superconducting films (of order 3000 A) in very strong magnetic fields. For magnetic fields in the range 250–500 kG, the sensitivity of the probe is 10−2 emu. Accuracy and high sensitivity were obtained by combining a sample extraction system, vibration isolation, and an inductive sensor with optimized flux coupling geometry. The magnetic flux coupling to the sensor was verified to exceed 70%, both by calculation and experimental calibration.

ARMS: A Successful European Program for an 80 T User Magnet

ARMS is the acronym for Advanced Research Magnet Systems, a project under the European Unions 5th Framework Research Infrastructures program (HPRI-CT-1999-50007). Eight partners throughout Europe cooperated in ARMS, which was coordinated by the University of Oxford, UK. The objective of the project was to build an 80 T user magnet to be installed at LNCMP, Toulouse, France. The approach chosen was the coil-ex/coil-in method, whereby a large outer coil was energized by LNCMPs unique, 14 MJ capacitor bank. The inner coil was energized by a fast, 100 kJ bank at the peak of the outer coils field. In this paper the evolution of the coils, the conductors and other materials is outlined as is the testing and ultimate, successful use in physics experiments up to 76 T. A view of the future direction of high pulsed fields in Europe, post-ARMS, will also be given

Observation of magneto-thermal instabilities in (YxTm1−x)Ba2Cu3O7 single crystals in pulsed magnetic field magnetization measurements

The understanding of flux jumps in the high temperature superconductors is of importance since the occurrence of these jumps may limit the perspectives of the practical use of these materials. In this work we present the experimental study of the role of heavy ion irradiation in stabilizing the HTSC against flux jumps by comparing un-irradiated and 7.5 · 1010 Kr-ion/cm2 irradiated (YxTm1−x)Ba2Cu3O7 single crystals. Using pulsed field magnetization measurements, we have applied broad range of field sweep rates from 0.1T/s up to 1800 T/s to investigate the behavior of the flux jumps. The observed flux jumps, which may be attributed to thermal instabilities, are incomplete and have different amplitudes. The flux jumps strongly depend on the magnetic field, on the magneto-thermal history of the sample, on the magnetic field sweep rate, on the critical current density jc, on the temperature and on the thermal contact with the bath in which the sample is immersed.

NEW NON-COOPERATIVE QUANTUM PHENOMENON IN A FERRIMAGNET WITH ANTIFERROMAGNETIC IMPURITY

The differential magnetic susceptibility of Gd0 01Y2.99Fe5O12 polycrystalline compounds is studied at the temperature range from 0.6 to 4.2 K in pulsed magnetic fields up to 50 T. It was observed that the magnetization of the compound with x = 0.01 shows a quantum (stepwise) behavior at T = 0.6 K in magnetic fields around 33 T. The Heisenberg model of a ferrimagnet with weakly coupled antiferromagnetic impurities is used to explain the obtained results. Following this model, the energy levels of the impurity ions become not equally spaced due to the magnon-magnon interaction between the iron spins and the rare earth spins. Increase of the external field leads to the crossover of the excited states with the ground one, which takes place in different fields. In result, several peaks of the magnetic susceptibility appear under a variation of magnetic field in the vicinity of a field, which is equal to the effective field of the Gd-Fe exchange interaction.

Observation of the peak effect at high fields in single crystalline YBa2Cu4O8

Abstract The peak effect in the magnetic hysteresis of an untwinned YBa 2 Cu 4 O 8 single crystal has been measured at temperatures down to 5 K, using a high sensitivity susceptometer in pulsed magnetic fields up to 50 T. The peak effect is due to an increase of the flux pinning as the magnetic field increases and results in a magnetisation hysteresis loop in the shape of a fishtail. The observed peak in the M ( H ) curve shows a clear temperature dependence in that the field B max at which the peak occurs increases with decreasing temperature.