High-Field Magnet

This custom built magnet was designed especially for Soft X-ray XMCD and XMLD measurements. The magnetic field of 9 Tesla along the beam direction can be ramped at 8 Tesla per minute, and a magnetic field of 4 Tesla perpendicular to the beam direction can be ramped at 2 Tesla per minute. However, we typically ramp at 3T/min along the beam and 1T/min perpendicular to the beam, though we can adjust the rate depending on the required fields and the experimental need.

The sample is vacuum-mounted onto a LHe variable temperature insert that can reach ~6 K, but should be improved in the near future to ~3K, and can go up to 325K. This insert can be rotated over 360 degrees about the vertical axis. The sample space is ultra-high vacuum (10-10 to 10-11 mbar base pressure with sample at room temperature), obtained by cryo-pumping of the liquid helium can. Absorption spectra can be simultaneously measured in drain current and total fluorescence yield mode, and if requested in transmission.


Samples

Samples need to have a minimum 0.7 × 0.05 mm (horizontal × vertical) measurement surface, for smaller sizes contact us in advance.
Since the beam spot dimensions are adjustable, spot sizes of up to several milimeters are also possible.
Polycrystalline samples need to be 3 mm thick so that they can be filed in vacuum to expose clean surfaces.
Single crystals that need to be fractured in vacuum need to be 5 mm high.
Single crystals that need to be sputter-cleaned can have up to 10 mm diameter, and be typically 2-3 mm thick.
 

Sample Holders

We have developed a range of sample holders in high-purity aluminum or copper. Samples can be glued or clamped down.
A special sample holder using Omicron plates for single crystals is available. Sample size can be anything between 2 mm and 14 mm.
The screws are molybdenum, and Omicron plates used are mostly tantalum, with tungsten or molybdenum plates also available. This is because they must be non-magnetic for use in the HFM

Sample Holder Type 1: Plate Screwed into Shuttle

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Sample Holder Type 2: Omicron Plate Slid into Shuttle

sample_holders_xmcd_omicron_plates.png
The Omicron plate dimensions are contained within this document - the plate is covered by 1mm at each end when slotted in the holders, thus the effective width of the plate is 16mm (2mm reduced).

Sample Preparation

We have built an improved sample preparation facility with dedicated chambers for thin-film growth, molecule deposition and sample characterisation.
These chambers are connected to the magnet via a transfer tunnel, and samples are transferred into the magnet with a vertically mounted magnetic transfer rod.
 
For more details please contact the beamline staff.