Skyrmion lattice in 4-electron magnet EuPtSi; Neutron scattering study

4電子磁性体EuPtSiにおける磁気スキルミオン格子; 中性子散乱による研究

金子 耕士   ; Frontzek, M. D.*; 松田 雅昌*; 伊藤 孝   ; 大石 一城*; 中尾 朗子*; 宗像 孝司*; 大原 高志   ; 垣花 将司*; 芳賀 芳範   ; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

Kaneko, Koji; Frontzek, M. D.*; Matsuda, Masaaki*; Ito, Takashi; Oishi, Kazuki*; Nakao, Akiko*; Munakata, Koji*; Ohara, Takashi; Kakihana, Masashi*; Haga, Yoshinori; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

The lack of spatial inversion symmetry in a structure gives rise to appearance of antisymmetric interactions, that may induce unconventional states of matter. In MnSi, an application of a magnetic field induces a new ordered state with magnetic skyrmions, particle-like topologically non-trivial spin textures. Whereas diverse properties of skyrmions have been revealed so far, materials hosting skyrmions were mostly limited to 3 electron systems. Our neutron diffraction experiments on new 4 electron magnet EuPtS indicate that the field-induced phase in this compound has a triple- magnetic structure in the plane normal to the applied field. Namely, the result suggests that EuPtSi is the first 4 electron magnet to host magnetic skyrmion lattice. The skyrmion in EuPtSi has distinct differences from 3 systems. One major difference is that EuPtSi has shorter periodicity. This originates in a relatively strong coupling to the lattice in EuPtSi, which may give an anisotropic magnetic phase diagram for the A phase. The present discovery in the 4 electron magnet will open new possibilities to deepen our understanding on skyrimion physics.