Magnetic-field-enhanced aniferromagnetism in the noncentrosymmetric heavy-fermion superconductor CePtSi

空間反転対称性の欠如した重い電子系超伝導体CePtSiにおける磁場増強反強磁性

金子 耕士   ; Stockert, O.*; Fk, B.*; Raymond, S.*; Skoulatos, M.*; 竹内 徹也*; 大貫 惇睦*

Kaneko, Koji; Stockert, O.*; Fk, B.*; Raymond, S.*; Skoulatos, M.*; Takeuchi, Tetsuya*; Onuki, Yoshichika*

The effect of magnetic field on the static and dynamic spin correlations in the non-centrosymmetric heavy-fermion superconductor CePtSi was investigated by neutron scattering. The application of a magnetic field B increases the antiferromagnetic (AFM) peak intensity. This increase depends strongly on the field direction: for the intensity increases by a factor of 4.6 at a field of 6.6T, which corresponds to more than a doubling of the AFM moment, while the moment increases by only 10% for at 5T. This is in strong contrast to the inelastic response near the antiferromagnetic ordering vector, where no marked field variations are observed for up to 3.8T. The results reveal that the AFM state in CePtSi, which coexists with superconductivity, is distinctly different from other unconventional superconductors.