Magnetic Structures in the Vicinity of the Pressure-Induced Superconducting Phase in CeNiC₂

The Ce-based non-centrosymmetric strongly correlated electron system, CeNiC₂, shows multiple magnetic phase transitions at low temperatures ^[1]. Most importantly, we have recently observed the pressured-induced heavy-fermion superconductivity in this compound below 3.5 K under 10.7 and 11GPa ^[2]. However, the magnetic structures of CeNiC₂ have not been well studied. In order to understand the superconducting pairing mechanism, it is important to characterize the magnetic structures in the vicinity of the superconducting phase. This talk will focus on the high-pressure magnetic structure study of CeNiC₂ based on our unpolarized and polarized neutron diffraction experiments using single crystals. An incommensurate antiferromagnetic phase (AFIC), in which the magnetic structure depends on pressure, is observed in a wide pressure range. The temperature and pressure dependent magnetic structures in the AFIC phase and their connections to the superconductivity will be discussed in detail.
[1] K. Motoya et al., J. Phys. Soc. Jpn. 66, 1124 (1997).
[2] S. Katano et al., Phys. Rev. B 99, 100501 (2019).