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Research in extremely high magnetic fields

Objective


According to researchers at the centre, the most significant work completed during this project was:

- Experiments with the intermetallic heavy fermion UPt3. This compound shows a metamagnetic transition at a magnetic field around 20T. Careful experiments at millikelvin temperatures, with an in-situ rotation of an extremely pure whisker of the material have allowed researchers to understand changes in the Fermi surface topology, by investigating the Shubnikov de Haas oscillations around the phase transition. These experiments helped clarify how the metal gradually loses the correlation underlying the heavy fermion character.

- The Fermi surface of several members of the quasi 2-D family of BEDT-TTF charge transfer salts could be determined through angle-dependent (and sometimes subkelvin) magnetotransport study of the Subnikov de Haas oscillations.
Especially intriguing was the nature of the kink field at around 22T in (BEDT-TTF)2KHg(SCN)4. These experiments contributed to the growing understanding of this family of compounds.
The University of Nijmegen, which runs this facility, granted a total of 320 magnet-hours per year to users in this project which represents roughly 25% of the facility's yearly magnet-hour capacity.

Total access by users in this project totalled 2060 magnet-hours between 1990 and 1993. To complete the 33 different experiments conducted, visiting scientists spent over 450 man-days with high field experiments. The results of this work appeared in more than 71 refereed journal publications.

Project coordinators reported that the demand for magnet time has been overwhelming, and that interest is growing - especially for access to the highest magnetic fields (up to 30 tesla) - for more sophisticated experiments involving the spectroscopic tools, and for the facilities which combine millikelvin temperatures with the highest magnetic fields.

European Commission grants have enabled significant improvements at the Nijmegen facility.

These included:

- Installation of climate control in two optics laboratories, bringer better stability and accuracy to the optical instruments.

- Installation of a 20-tesla Bitter Magnet and of a 17.5-tesla superconducting magnet.

- Purchase of an additional helium transport vessel, bath cryostat, custom-designed cryostat inserts, and high vacuum equipment. This maintained the very high level of the centre's cryogenic facilities.

- Upgrading of the facility's computer-aided data acquisition, data communication and processing infrastructure.

Investments were also made in electronics and optic equipment.

The experiments done by research teams during this project cover several areas: magnetotransport; optical studies of semiconductors and organic conductors; studies of superconductors, and of heavy-fermion compounds; quantum fluids and the clustering properties of magnetic ions dispersed in glasses.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

STICHTING KATHOLIEKE UNIVERSITEIT
Address
Toernooiveld 1
PO Box 9010 Nijmegen
Netherlands