Investigation of incommensurate structures in GdCo2B2

GdCo2B2 is a magnetocaloric material which is currently being developed for use in the hydrogen liquefaction process. It is an antiferromagnetic magnetocaloric material which exhibits four transitions in a narrow temperature region. While these transitions are thought to play a major role as part of the mechanism of the magnetocaloric effect, the magnetic structures are not yet understood.
Recent high-energy neutron diffraction measurements indicated the presence of several complex incommensurate structures in the system, which could potentially be related to Skyrmions. Several propagation vectors are possible, but it has not yet been possible to differentiate between the various structures. To identify the propagation vectors for the various structures it is proposed to access the (000) + k reflections. These reflections, which pattern simulations indicate are present at large d-spacings of up to 60 Å, can be measured on the instrument WISH by operating it in the double frame mode. As the material contains highly absorbing elements, a test run was done using WISH to confirm the viability of the experiment. By mounting the sample in reflection mode, the paramagnetic system was successfully recovered. Three days of beamtime are requested to measure all of the complex magnetic structures of this system using the reflection and double frame modes on WISH.