Hiroyuki Nojiri (SIMES Seminar)

Date/Time
Date(s) - Feb 14 2014
11:00 AM - 11:00 AM

Location
Shasta Room, Bldg. 40, Room 361

Category(ies)


Application of pulsed magnetic fields for X-ray spectroscopies  and neutron diffraction

Professor Hiroyuki Nojiri

Institute for Materials Research, Tohoku University, Japan

 

X-ray spectroscopy and Neutron diffraction are unique tools for investigating magnetic and electronic states of condensed matters. In high magnetic fields, various exotic states are induced. The order parameters and the essential characteristics can be examined by X-ray and neutron. Use of high magnetic fields in the beam facilities had been limited for the large size of magnets.  Recently, we have developed a compact and portable pulsed field generator and a cryostat system to conduct experiments in 30-40 T[1]. The portability enables us to perform varieties of experiments in different facilities around the world. In this talk, the present status of X-ray spectroscopy and neutron diffraction in high magnetic field is reviewed.

(1)  X-ray spectroscopy

X-ray absorption spectroscopy can been used to investigate the electronic state by element selective manner in high magnetic fields. For example, the valance state of rare-earth ions was determined by using a hard-X-ray spectroscopy[2]. More recently, the use of soft-X-ray becomes possible, which widen the application of X-ray spectroscopy to 3d transition metal ions[3]. The determination of the element and orbital selective magnetic polarization has been made by using a X-ray circular dichroism: XMCD[4]. The most important merit to use the high magnetic field in XMCD is that a larger moment is induced. This feature extends the application of XMCD for varieties of materials including paramagnets and antiferromagnets.

(2)Neutron Diffraction

Neutron diffraction is the most direct and the powerful mean to determine a magnetic structure. In reactor source, monochromatic neutron is used and thus magnetic field dependence of a Bragg peak is measured in each magnetic field pulse. A typical number of field generation is 100-200 with the interval of 5 minutes at 30 T[5]. Use of polarized neutron is also possible because of the monochromatic beam.

In pulsed white neutron, Laue method can be used to scan a wide range in reciprocal space. The change of magnetic structure such as the shift of incommensurate peak can be traced efficiently[6]. Moreover, the number of field shot can be reduced for the strong instantaneous pulse intensity. At present 30 T and 40 T are available at SNS and ISIS, respectively. In the J-PARC, a 50 T magnet driven by a middle size 250 kJ capacitor bank is installed and used.

In addition, the system can be used for various table top experiment such as ultra-fast spectroscopies[7].

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.