[Title]
Direct Observation of Universal Spin-Lattice Interaction in Frustrated Magnet by using Ultrahigh Magnetic Field Neutron Diffraction

[Summary]
A joint research group led by Professor Hiroyuki Nojiri (Institute of Materials Research, Tohoku University), Senior Scientist Masaaki Matsuda (Japan Atomic Energy Agency), and Assistant Professor Hiroaki Ueda (Institute for Solid State Physics, the University of Tokyo) has succeeded in the neutron diffraction in ultrahigh magnetic fields up to 30 Tesla, and found that frustrated chromium spinel system has the universal magnetic structure at the half-plateau phase. The present result shows that a universal spin-lattice interaction plays an important role in this phenomenon. It would contribute to the understanding of the spin-lattice coupling in frustrated antiferrromagnet.

The developed high magnetic field neutron diffraction system is useful for the microscopic study of various magnets. It would contribute to the development of new magnetic materials such as multi-ferroic compounds and nano magnetic particles.

Keywords
[Study on Frustrated Magnet]

Properties of matters are mostly closely related with the behaviors of electrons, which have small magnets called spin. Hence, a state of matter can be precisely controllable by magnetic fields.

Frustrated magnets have various magnetic states with degeneracy and it is difficult to make a prospect of magnetic states in different conditions. By using a magnetic field, it is possible to tune the frustration, which may stabilize a non-trivial state. In the present study it is shown that frustrated chromium spinel has the common magnetic structure in magnetic fields. It indicates that the universal spin-lattice interaction mechanism plays an important role.

[Neutron diffraction method under ultrahigh magnetic fields]
Neutron diffraction is the most powerful method to determine spin structure. It has been desired to use this method to study magnetic states in high magnetic fields. The developemnt for neutron diffraction method under ultrahigh magnetic fields have been continued for more than 20 years. Our recent success at more than 30 Tesla are attracting great attentions from the community. This achievements have been made by combining original minimagnet to generate pulsed ultrahigh magnetic fields and a neutron diffraction reactor at Institute for Laue Langevin, France that is the world’s strongest research neutron reactor.

A research group led by Professor Nojiri has developed this original device to generate pulsed ultrahigh magnetic fields. The device has been used in various countries because quick experiments are possible without modifications of exiting experimental instruments. Tohoku University and Japan Atomic Energy Agency have developed this ultrahigh magnetic field neutron diffraction device for 4 years at JRR-3, a research reactor, at Institute for Nuclear Science, Tokai Research and Development Center. The present case is the first technical transfer to the other country. The newly developed device has attracted attentions for its performance under ultrahigh magnetic fields.

The new method is expected to be applied to various magnetic substances for the development of magnetic materials.

The research result is expected to contribute to the new design and development of magnetic materials adding to basic physics. The achievements have been published online in Physical Review Letters, a well-known academic journal, on January 26, 2010. Paper’s title is Universal magnetic structure of the half-magnetization phase in Cr-based spinels._

[Contact]
Professor Hiroyuki Nojiri
Institute of Materials Research, Tohoku University
Address: 2-1-1 Katahira Aoba-ku Sendai, Miyagi, Japan
Tel: +81-22-215-2015, Fax: +81-22-215-2016
E-mail: nojiri@imr.tohoku.ac.jp

Associate Professor Kenji Ohoyama
Tel: +81-22-215-2038, Fax: +81-22-215-2036
E-mail: ohoyama@imr.tohoku.ac.jp