High-Field Diffractometer

Endstation for Dichroic Soft X-ray Absorption and Scattering Experiments in High Magnetic Fields

The High-Field Diffractometer is an endstation for both soft-x-ray absorption (XAS)  and resonant soft x-ray scattering (RSXS) in magnetic fields up to 7 Tesla and temperatures down to 4 K. This combination of high magnetic fields and low temperatures renders the setup ideal for studying weakly coupled magnetic systems like diluted magnets or single molecular magnets. The unique feature of this endstation is an in-vacuum superconducting coil that can be rotated independently from the sample. The station is therefore perfectly suited for XMCD and XMLD experiments in various geometries. The absorption signal is typically measured in the TEY-mode via the sample drain current. Employing continuous mode, a pair of energy-dependent absorption scans with opposite light helicities can be recorded with very high quality within less than 10 minutes. Depending on the sample, noise ratios as low as 10-4 can be achieved. A rotatable photon detector enables to perform dichroism experiments using specular reflectivity, which is often more sensitive to tiny magnetizations at interfaces and less surface sensitive than TEY-mode experiments. The same detector permits RSXS experiments at relevant scattering geometries to study the evolution of electronic ordering phenomena, like charge and orbital ordering in high magnetic fields, being at the heart of many of todays most fascinating macroscopic phenomena in complex oxides. Samples are transferred in a  fast and reliable way from outside vacuum to a sample holder directly attached to a LHe-flow cryostat that provides the base temperatures of 4 K. The endstation is permanently attached to the UE46_PGM1 beamline providing high photon flux between 120eV and 2000 eV and variable photon polarization. The beamline also hosts the XUV Diffractometer, an instrument dedicated to high performance RSXS studies. Both instruments can be used within the same beam time. Beamline and instruments are operated by the Department Quantum Phenomena in Novel Materials at HZB.


Selected Applications

  • Diffraction from complex electronic superstructures (magnetic, charge and orbital order)
  • Magnetization states of single molecular magnets
  • Element-specific magnetic hysteresis loops (switching behavior in heterostructures or alloys, exchange bias)
  • Electronic ground states in crystals
Magnet angles and slits to estimate possible x-ray scattering geometries (courtesy A. Frano).

Magnet angles and slits to estimate possible x-ray scattering geometries (courtesy A. Frano).

Station data
Monochromator PGM
Experiment in vacuum yes
Temperature range 4 - 350 K
Detector AXUV100 type photodiode
Manipulators
Magnetic Field standard: 6 Tesla (for fields up to 7 Tesla contact Station Managers)
Magnetic Field Geometry horizontal, rotatable (90 deg.) with respect to sample
Scattering Geometry horizontal
Sample rotation 0 deg. to 90 deg. with respect to the photon beam
Scattering angles limited, depending on orientation of the magnet
Software SPEC
Phone Number (8062) 14717

Methods

XMLD, XMCD, REXS, Magnetic Scattering

Selected Publications