Magnetism and Superconductivity – University of Copenhagen

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X-Ray and Neutron Science > Research > Magnetism and Supercon...

The multiferroic material TbFeO3 has a peculiar magnetic structure at temperatures just around 3 K (minus 270 C). It is locally ferromagnetic, but breaks up into domain of exactly equal sizes and shapes. The picture shows the resulting neutron diffraction signal for different temperatures.

Magnetism and Superconductivity

The X-Ray and Neutron Science Section has a broad activity within the fundamental study of magnetic and superconducting systems that also have a potential for applications.

Magnetic materials have fascinated people in thousands of years and are in abundant everyday use. In addition, studies of magnetic systems have often elucidated general properties of materials, e.g. phase transitions. We study novel magnetic materials both to find new general insight in the physics of materials and to permit further research in material types with potential applications.

Most of our projects involve frequent use of neutron scattering, and possibly X-ray scattering and measurements of materials' resistitivity, heat capacity, and magnetic susceptibility. The projects often involve a large degree of collaboration with the activity in the Condensed matter theory research section and other activities in the X-ray and Neutron Science group.

Specific projects include:

  • Studies of quantum effects in low-dimensional magnets, revealing effects of many-body quantum mechanics.
  • General studies of quantum phase transitions - phase transitions that occur at the lowest reachable temperatures and are governed by quantum fluctuations.
  • Studies of magnetic "frustration", where the atomic magnetic moments experience contradicting interactions from its surroundings. This effect has a potential use in magnetic refrigeration.
  • Studies of magnetic nanoparticles and molecules. The effects of the finite size of the systems are investigated to elucidate possible applications in novel magnets and/or data storage.
  • Studies of multiferroic materials, where magnetic order coincides with lattice deformation and ferroelectric order. In these materials, magnetism can be induced by pressure or an electrical field and vice versa. These materials display a wealth of fundamentally interesting physical phenomena, but they also have a large potential to become the main component in sensor and electric-magnetic data storage devices.
  • Investigations of high-temperature superconductors that have zero resistivity below a certain temperature. The origen of superconductivity in these materials remains a puzzle to science. We investigate the magnetic properties of superconductors to see if they are related to their inherent quantum magnetism and a possible quantum phase transition.

For further information: Contact Kim Lefmann (lefmann@nbi.ku.dk)