Ferromagnetic Instability in AFe4Sb12 (A = Ca, Sr, and Ba)

Magnetic, transport and thermal properties of AFe4Sb12 (A = Ca, Sr, Ba) are reported. All three compounds show a maximum in both the magnetic susceptibility and thermopower at 50 K, and a large electronic specific heat coefficient of 100 mJ/mol K2. These properties are the characteristics of a nearly ferromagnetic metal. Furthermore, a remanent moment of the order of 10-3muB/Fe was observed below 54, 48, and 40 K for A = Ca, Sr, and Ba, respectively. The volume fraction of the ferromagnetic component was estimated to be 10-20% by zero-field muSR measurements.