UE46_PGM-1 Beamline

UE46_PGM-1 is one of two beamlines situated at the elliptical undulator UE46. The beamline provides soft x-rays with tunable polarization (linear, circular) in the energy range between 120 eV and 2000 eV. It has a plane-grating design, the last mirror chamber hosts two mirrors that can be switched to provide a focussed or collimated beam. Techniques employed at UE46_PGM-1 include polarization-dependent x-ray absorption and resonant soft x-ray scattering experiments, covering a wide range of materials and scientific problems. Continuous-mode scanning is implemented at the beamline, a pair of energy-dependent x-ray 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. The beamline hosts two permanent endstations, the XUV Diffractometer, an instrument dedicated to high performance RSXS studies and the High-field Diffractometer, an instrument for RSXS and XAS studies in magnetic fields up to 7 Tesla. Both instruments can be used within the same beam time. Beamline and instruments are operated by the Institute Quantum Phenomena in Novel Materials at HZB.

Selected Applications

• Resonant diffraction from magnetic, charge, and orbital order superstructures
• Spectroscopy of electronic ordering phenomena
• Magnetization states of single molecular magnets
• Element-specific magnetic hysteresis loops
• Magnetization depth profiles

UE46-PGM1 beamline and endstations.

XUV Diffractometer for Resonant Soft X-Ray Scattering

The XUV Diffractometer is a dedicated endstation to explore electronic ordering phenomena, like magnetic, charge and orbital ordering by resonant soft x-ray scattering (RSXS) experiments. This versatile endstation is a UHV-compatible two-circle diffractometer operating in horizontal scattering geometry with the sample and detector rotations driven from outside vacuum by Huber circles with highest accuracy and stability. It allows to perform high quality diffraction experiments even from tiny crystals (< 100μm x 100μm) over a large angular range as well as measurements of specular reflectivity with very high accuracy. With the samples mounted directly to a LHe-flow-cryostat, sample temperatures below 4 K can be reached. Azimuthal rotation in situ is provided for azimuth-dependent measurements. Photons are detected by an AXUV100-type photodiode with a set of changeable slits in front for optimizing the q-resolution. The detector can be scanned in the direction perpendicular to the scattering plane. This allows to compensate possible Chi-misalignment without compromising about the lowest sample temperatures. The experimental setup allows for x-ray absorption (XAS) masurements by parallel monitoring of the sample drain current (TEY measurements) as well as for FY measurements. The instrument is flexible and can adapt to special sample mounting. The endstation is permanently attached to the UE46_PGM-1 beamline providing high photon flux between 120eV and 2000 eV and variable photon polarization. The beamline also hosts the High-Field Diffractometer, an instrument for RSXS and XAS studies in magnetic fields up to 7 Tesla. Both instruments can be used within the same beam time. Beamline and instruments are operated by the Institute Quantum Phenomena in Novel Materials at HZB.

Selected Applications

• Diffraction from complex electronic ordering phenomena (magnetic, charge and orbital order )
• Interfacial electronic properties in heterostructures
• Magnetic structure determination even from tiny single crystals and nanostructures
• Magnetization depth profiles

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 Institute 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).