Single crystal neutron diffraction study of the magnetic structure of TmNi2B2C

Neutron diffraction techniques have been used to study the magnetic structure of single crystals of the magnetic superconductor (Tc congruent 11 K) TmNi2B2C. We find that below approximately 1.5 K the magnetic moments order in an incommensurate spin wave with propagation vector qm=qm(a*+b*) [or qm=qm(a*-b*)] with qm=0.094±0.001. The spin wave is transverse with the moments aligned along the c axis, and the observation of relatively intense higher-order harmonics shows that the modulation is not purely sinusoidal but considerably squared. This incommensurate magnetic structure, which coexists with superconductivity below TN congruent 1.5 K, is quite different from those observed in the magnetic superconductors HoNi2B2C and ErNi2B2C. The origin of diffraction peaks observed in scans parallel to a* is briefly discussed. copyright 1997 American Institute of Physics