Magnetic susceptibility and superconductivity of single-crystal Ho-Mo-S Chevrel phase

Single crystals of the Chevrel phase holmium molybdenum sulfide of approximately 0.15 mm on edge have been grown in sealed molybdenum crucibles. On the bases of microprobe and full x-ray structure analysis we find a large range of Ho concentration. Susceptibilities were measured on crystals oriented with the hexagonal c axis parallel to the applied magnetic field in the temperature range 5 to 200 K using a SHE SQUID magnetometer and a force balance. We observed a paramagnetic Curie Weiss behavior in this temperature interval with θ≊0 K and a molar Curie constant about a factor of 2 larger than the expected theoretical value of 14.1. The large value of CM suggests that the Ho spins are constrained by the crystal field to the c axis. The perpendicular susceptibility is extremely small. A superconducting transition at ∼2.4 K is measured in low fields by an ac SQUID technique.