Magnetic-field-dependent susceptibility of single-crystal Ho-Mo-S Chevrel phase at very low fields

We report measurements of the temperature dependence of the ac and dc susceptibility of single-crystal HoMo6S8 oriented both parallel and perpendicular to the magnetic axis in static magnetic fields varying from 0.005 to 100 Oe. We find Tc1 ≅1.70 K and T c2 ≅0.65 K with significant supercooling in low fields at T c1 and very long time effects associated with cooling through T c2 but not on warming. We find a significant difference between the ac and dc susceptibility changes at both transitions. The lower critical field Hc1 is determined to be ∼20 Oe.