149Sm nuclear resonant scattering of SmB2C2

The quantum beat spectra due to magnetic ordering can be observed below the 51 K upper transition temperature of SmB2C2 using the nuclear resonant forward scattering technique with the 149Sm nuclei. The spectrum without dynamical or quantum beats can be observed at 60 K. This result indicates that the magnetic interaction continues to exist above 51 K. Examinations of the diffuse magnetic scattering of neutrons from HoB2C2 show a similar continuation of the magnetic interaction above the Neel temperature. It appears that the spectrum at 60 K is caused by a distribution of the hyperfine magnetic field