Magnetic Properties of Manganese Formate Dihydrate below 1°K

抄録

The magnetic susceptibility of powder and single crystal manganese formate has been measured in the temperature region between 0.1°K and 1.5°K. Powder susceptibility between 1.5° and 0.7°K gives a Curie-Weiss law, 0.6C⁄(T+0.2), where C is Ng²β²S(S+1)⁄3k. Single crystal susceptibilities show a small anisotropy at this temperature region. These facts can be regarded as an evidence for the remaining of paramagnetic spins after the previously reported two transitions at 3.7°K and at 1.7°K. At about 0.6°K another transition has been observed in addition to the above mentioned ones. This newly observed transition indicates the ordering of the residual free spins.