Unique helical magnetic order and field-induced phase in Trillium lattice antiferromagnet Euptsi

Koji Kaneko, Matthias D. Frontzek, Masaaki Matsuda, Akiko Nakao, Koji Munakata, Takashi Ohhara, Masashi Kakihana, Yoshinori Haga, Masato Hedo, Takao Nakama, Yoshichika Ōnuki

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Abstract

Magnetic transition phenomena in cubic chiral antiferromagnet EuPtSi with TN = 4.0 K were investigated by means of single crystal neutron diffraction. At 0.3 K in the ground state, magnetic peaks emerge at positions represented by an ordering vector q1 ¼ ð0:2; 0:3; 0Þ and its cyclic permutation. Upon heating, an additional magnetic peak splitting with hysteresis was uncovered at around TN 2:5 K, indicating the presence of a first-order commensurate–incommensurate transition with q1 ¼ ð0:2; 0:3; Þ (δmax ’ 0.04) at TN. A half-polarized neutron scattering experiment for polarization parallel to the scattering vector revealed that polarization antiparallel to the scattering vector has stronger intensity in both magnetic phases. This feature clarifies the single chiral character of the helical structure with moments lying perpendicular to the ordering vector in both ordered states. Under a vertical magnetic field of 1.2 T for B k ½1; 1; 1 at 1.9 K entering into the so-called A phase, magnetic peaks form characteristic hexagonal patterns in the equatorial scattering plane around nuclear peaks. An ordering vector qA ’ ð0:09; 0:20; 0:28Þ of the A-phase has similar periodic length as q1, and could be the hallmark of a formation of skyrmion lattice in EuPtSi.

Original languageEnglish
Article number013702
JournalJournal of the Physical Society of Japan
Volume88
Issue number1
DOIs
StatePublished - 2019

Funding

We acknowledge T. Nakajima, K. Ohishi, T. U. Ito, T. Sakakibara, T. Takeuchi, Y. Homma, T. Matsumura, H. Nakao, C. Tabata, and R. Shiina for stimulating discussions. The authors thank the sample environment groups at HFIR, ORNL, and MLF J-PARC for their support on the neutron scattering experiments. This work was partly supported by MEXT=JSPS KAKENHI Grant Numbers JP16K05031 (Scientific Research (C)) and JP18H04329 (J-Physics), and used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. WAND and its successor WAND2 are operated jointly by ORNL and Japan Atomic Energy Agency under US\u2013Japan Cooperative Program on Neutron Scattering. The neutron diffraction experiment on SENJU at MLF J-PARC was performed under a user program (Proposal No. 2018A0221).

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