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

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

Physical Review B, 89(24), p.241105_1 - 241105_5, 2014/06

AA2014-0242.pdf:0.39MB

https://doi.org/10.1103/PhysRevB.89.241105

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.

Effect of magnetic field on antiferromagnetism in non-centrosymmetric heavy-fermion superconductor CePtSi

金子 耕士; Stockert, O.*; Arndt, J.*; Borth, R.*; Skoulatos, M.*; Habicht, K.*; Kiefer, K.*; Schneidewind, A.*; Etzdorf, D.*; 竹内 徹也*; et al.

no journal, , 

The heavy-fermion superconductivity in CePtSi with a non-centrosymmetric structure attracts a lot of attention since novel superconducting properties are expected under this symmetry. Another characteristics of the superconductivity in CePtSi is its coexistence with long-range antiferromagnetic order. Therefore detailed antiferromagnetic properties and its interplay with superconductivity are of strong interest to investigate. The magnetic structure of CePtSi is represented by =(0,0,1/2). We have observed that the 0 0 1/2 antiferromagnetic reflection exhibits a peculiar response to an external magnetic field; its intensity increases with magnetic fields. These results imply unusual antiferromagnetism in CePtSi.

Effect of magnetic field in non-centrosymmetric heavy-fermion superconductor CePtSi

金子 耕士; Stockert, O.*; Skoulatos, M.*; Schneidewind, A.*; 竹内 徹也*; 松田 達磨; 芳賀 芳範; 摂待 力生*; 大貫 惇睦; 目時 直人

no journal, , 

CePtSi without inversion symmetry exhibits an antiferromagnetic (AFM) order at 2.2 K and enters into a heavy-fermion superconducting state below 0.5 K. Additional anomalies inside the AFM state were found under external magnetic fields in the vicinity of the upper critical field of the superconducting state. Our neutron scattering experiments under magnetic fields revealed that the application of the magnetic fields leads to an enormous enhancement in the AFM peak intensity in CePtSi, opposite to what is observed in usual antiferromagnets. We have clarified that the reported anomaly under the magnetic fields corresponds to inflection points in the field variation of the AFM intensity. The observed huge increase in AFM intensity corresponds to an increase of the ordered moment under the magnetic fields. These results imply an existence of a missing magnetic response in the ground state, which might be related to the formation of the superconducting state in CePtSi.