NEUTRON-SCATTERING STUDIES OF THE COEXISTENCE OF LONG-RANGE MAGNETIC ORDER AND SUPERCONDUCTIVITY IN DY1.2MO6S8 AND TB1.2MO6S8

Both Dy1.2Mo6S8 and Tb 1.2Mo6S8 are superconducting below T c=2.05 K. Neutron scattering studies show that these compounds in zero applied magnetic field develop long-range antiferromagnetic order (greater than 300 Å) at TM=0.4 K and TM=1.0 K, respectively, which does not destroy the superconducting state. Magnetization measurements at temperatures below TM suggest the development of ferromagnetic order as the applied magnetic field increases. In the case of Tb1.2Mo 6S8 the neutron data show long-range ferromagnetic order developing for H?Hc2=1.9 kOe where Hc2 is the upper critical field for superconductivity. However, for Dy1.2Mo 6S8 long-range ferromagnetic order begins to develop at H=200 Oe, a field much less than Hc2=1.2 kOe. As the ferromagnetic intensity increases, the antiferromagnetic intensity decreases. Between H=200 Oe and H=1.2 kOe both ferromagnetic and antiferromagnetic order occur with the sample in the superconducting state.