同步輻射研究中心中子小組

SIKA user, Prof. Bing Li (Institute of Metal Research, Chinese Academy of Sciences) and his multinational collaborators published their study in Nature on March 28. They report on an unusual phase transition in a plastic crystal. The colossal barocaloric effects, reported here in a class of highly disordered solid, could be a solution to the next-generation of solid-state refrigeration technologies. Using neutron scattering instruments at J-PARC (Japan Proton Accelerator Research Complex) and ANSTO (Australia’s Nuclear Science and Technology Organisation), the team monitored the molecular dynamics of this material. Their experimental results and computer simulations are consistent. At the early stage of this research, SIKA instrument scientist, Dr. Shin-ichiro Yano (NSRRC) identified an anomaly in the incoherent elastic scattering intensity at the structural phase transition and confirmed hydrogen bonds as a key role in this effect after conducting neutron scattering experiments on SIKA.

SIKA, a cold neutron triple-axis spectrometer, is designed for studies in low-energy excitations; it is an effective tool to understand novel ground states of materials, such as superconductors, other strongly correlated systems, low dimensional magnets, etc. It is the Taiwan-Australian neutron instrument, built at ANSTO, based on the “Agreement on Neutron Beam Applications Research” signed between the National Science Council (NSC, Taiwan) and Australia in 2005. In 2013 NSRRC was commissioned by the NSC (later reorganized to Ministry of Science and Technology, MOST) to operate SIKA.

Nature volume 567, pages 506–510 (2019)

Prof W.F. Pong, from Tamkang University in Taiwan, along with collaborators from ANSTO and Osaka University in Japan, published the first research paper from the cold neutron, triple axis spectrometer, Sika.  

Just published in the Physical Review B, Prof. Pong used the neutron Spectrometer at OPAL to investigate the spatial spin-spin correlations and the spin relaxation processes in a single crystal of (Ni_0.4Mn_0.6)TiO₃. 

The parent compounds of this solid solution are antiferromagnetic with orthogonal easy axes of magnetisation.  When mixed at this 40/60 ratio the long range magnetic order is supressed and a glassy magnetic groundstate is formed, possibly hosting magnetic texture, such as a skyrmion with possible technological applications for spintronics. 

Using Sika, the team worked on the dimensionality of the spin-spin correlations and the universality class of the spin system.  It was found that the spatial correlations are over three times greater in the plane than out, but the relaxation processes in the two directions were within experimental error of each other.

The full reference is “Correlations and dynamics of spins in an XY-like spin-glass (Ni_0.4Mn_0.6)TiO₃ single crystal system”, R. S. Solanki, S. -H. Hsieh, C. H. Du, G. Deng, C. W. Wang, J. S. Gardner, H. Tonomoto, T. Kimura and W. F. Pong

Phys. Rev. B 95, 024425 (2017)

DOI:https://doi.org/10.1103/PhysRevB.95.024425

On Friday the 12th of June, the Australian Radiation Protection and Nuclear Safety Agency has given approval to commence user and commercial operations on SIKA cold neutron triple axis spectrometer.

User experiments approved following the Program Advisory Committee meeting in May 2015 can now be scheduled.

This demonstrated our commitment to service for Taiwan neutron research.

The SIKA cold-neutron 3-axis spectrometer, which is operated by the NSRRC, has taken its first neutron scattering patterns.  A diffraction pattern of a common standard Ni was first measured in diffraction mode before the 3^rd axis was added to produce an inelastic neutron scattering spectrum of a crystal-field excitation in PrFeO₃. 

A fixed incident energy of 5.11 meV was used and the spectrum shows a scan of the final energy, with the excitation at an energy transfer of around 2 meV.