Magnetic Susceptibility of Ferrous Ammonium Tutton Salt at Liquid Helium Temperatures

Abstract

The magnetic susceptibility of ferrous ammonium sulfate hexahydrate has been measured between 0.95 and 4.2°K by both the Faraday and the ballistic mutual inductance bridge methods. At 4.2°K the susceptibility is (1.45±0.05)×10—3 emu/g, close to the value given by the high temperature Curie-Weiss law, 9.71×10—3/(T+3.2). Below 2°K the susceptibility is constant at (1.85±0.05)×10—3 emu/g. The results are shown to be compatible with available specific heat data in the low temperature region, provided that the lowest level is taken to be a singlet and the constant susceptibility is ascribed to temperature-independent paramagnetism of the lowest level.