Page 38 - ILLS Annual Report 2018

MAGNETISM
Noriki Terada. Japanese
National Institute for Materials Science, Japan
‘I am a senior scientist working at NIMS, Tsukuba, Japan. I am mainly studying pressure effects on strongly correlated electron systems including multiferroic materials. Recently,
I developed a non-magnetic Hybrid Anvil Cell
for Spherical Neutron Polarimetry experiments, based on collaborations with the ILL and JAEA, Tokai.’
Spherical neutron polarimetry under high pressure for a multiferroic delafossite ferrite
Spin-polarised hot-neutron diffractometer D3
The analysis of three-dimensional neutron
spin rotation at the interaction with a sample, using a technique referred to as spherical neutron polarimetry (SNP), is a very powerful means of determining complex magnetic structures in magnetic materials. In the present study, we successfully carried out the first
SNP experiment under high pressure up to
4.0 GPa on the D3 instrument, studying
the magnetoelectric multiferroic delafossite CuFeO2. The results presented here demonstrate that SNP measurements are feasible under high-pressure conditions, and that this
method is a useful approach to studying pressure-induced physical phenomena.
AUTHORS
N. Terada (National Institute for Materials Science, Japan) N. Qureshi (ILL)
L.C. Chapon (Diamond Light Source, UK)
T. Osakabe (Japan Atomic Energy Agency, Japan)
ARTICLE FROM
Nat. Commun. (2018)—doi: 10.1038/s41467-018-06737-6
REFERENCES
[1] F. Tasset, Physica B 156−57 (1989) 627
[2] N. Terada, D.D. Khalyavin, P. Manuel, T. Osakabe, P.G. Radaelli
and H. Kitazawa, Phys. Rev. B 89 (2014) 220403(R)
[3] N. Terada, J. Phys. Condens. Matter 26 (2014) 453202
[4] N. Terada, N. Qureshi, L.C. Chapon and T. Osakabe, Nat.
Commun. 9 (2018) 4368
Since Tasset developed the ILL’s CRYOgenic Polarisation Analysis Device (CRYOPAD), which enables three- dimensional neutron polarisation analysis [1], the SNP technique has been used to determine precise spin orientations in complex magnetic structures. In unpolarised neutron diffraction experiments, one needs to collect many magnetic Bragg peaks from different sample positions to perform the standard refinement procedure. In contrast, with the SNP method the so-called polarisation matrix of one Bragg reflection contains an enormous amount of information concerning the magnetic structure; therefore, generally the measurement of just a few reflections yields very precise results. However, since the CRYOPAD requires zero-magnetic field conditions in conjunction with superconducting Meissner screening to avoid neutron depolarisation [1], inside the magnetic vacuum it is necessary to use equipment, such as high-pressure cells, that are made of non-magnetic materials. To date, SNP experiments under high pressures have not been carried out because of this difficulty.
In the present study, we used a newly developed, non-magnetic Hybrid Anvil high-pressure Cell (HAC) (figure 1, left) to overcome this challenge. We employed a combination of a single sapphire crystal and a non-magnetic diamond composite (with an SiC binder) or WC with a non-magnetic Ni binder as the
ANNUAL REPORT 2018
Figure 1
left) Non-magnetic Hybrid Anvil Cell with diamond composite and sapphire anvils.
right) Magnetoelectric phase diagram of multiferroic delafossite ferrite CuFeO2 [4].