Application of Pulsed Magnetic Fields for X-ray Spectroscopies and Neutron Diffraction

by Hiroyuki Nojiri (Institute for Materials Research, Tohoku University)

Tuesday 18 Mar 2014, 15:30 → 17:00 Europe/Berlin

Building 25b | Room 109 (DESY Hamburg)

Application of Pulsed Magnetic Fields for X-ray Spectroscopies and Neutron Diffraction Hiroyuki Nojiri, Institute for Materials Research, Tohoku University X-ray spectroscopy and neutron diffraction are unique tools for investigating the magnetic and electronic states of condensed matter. In high magnetic fields, various exotic states can be induced, but the magnets' large sizes have limited their use. Recently, we have developed a compact and portable pulsed-field generator and cryostat system for conducting experiments in 30-40 Tesla (T) magnetic fields. The portability of our system enables us to perform a variety of experiments in different facilities around the world and in various table-top experiments, such as ultra-fast spectroscopies. X-ray absorption spectroscopy in high magnetic fields can investigate the electronic state in an element-selective manner. For example, hard-X-ray spectroscopy can determine the valance state of rare-earth ions, and soft X-rays can extend this technique to 3d transition metal ions. X-ray circular dichroism (XMCD) can determine element- and orbital-selective magnetic polarization. High magnetic fields induce larger moments in XMCD, thus expanding its use to a wide variety of materials, including paramagnets and antiferromagnets. Neutron diffraction is the most direct and powerful means for determining magnetic structures. Reactor sources produce monochromatic neutrons, so the magnetic field dependence of a Bragg peak is measured in each magnetic field pulse. Polarized neutron beams are also possible. Pulsed "white" (continuous in energy) neutron sources can trace changes in magnetic structure efficiently over a wide range in reciprocal space. Moreover, strong instantaneous pulse intensities can reduce number of field shots. At present, 30 T and 40 T magnetic fields are available at the Spallation Neutron Source in Tennessee and the ISIS spallation neutron facility in England, respectively. In the Japan Proton Accelerator Research Complex, a 250 kJ capacitor bank drives a 50 T magnet. References [1] Y. Narumi et al Synchrotron Radiat. News 25(2012) 12. [2] Y. H. Matsuda et al. J. Phys. Soc. Jpn. 77 (2008)054713. [3] T. Nakamura et al. Appl. Phys. Express 4(2011) 066602. [4] Y. Siratsuchi et al. Appl. Phys. Lett. 100, 262413 (2012) [5] K. Kuwahara et al. Phys. Rev. Lett. 110(2013) 216406. [6] H. Nojiri et al. Phys. Rev. Lett. 106(2011) 237202. [7] T. Noe et al. Rev. Sci. Instrum. 84(2013)123906.