OBSERVATION OF OSCILLATORY MAGNETIC ORDER IN THE ANTIFERROMAGNETIC SUPERCONDUCTOR HONI2B2C

The nature of the holmium order in the reentrant superconductor (Tc=7.5K) HoNi2B2C is revealed by neutron scattering. Upon cooling a transversely polarized oscillatory magnetic state is formed (TM8 K), characterized by a wave vector (0,0,qc) where qc0.05 -1 is only weakly dependent on temperature and field. At the reentrant superconducting transition (∼5 K) the amplitude of the oscillatory state abruptly decreases in favor of a commensurate antiferromagnet, whereby superconductivity is restored and coexists with antiferromagnetism at low temperatures. © 1994 The American Physical Society.