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

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.