Magnetic properties of ytterbium gallium garnet between 44 mK and 4K

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Abstract
Specific heat, magnetisation and susceptibility measurements on a single crystal of ytterbium gallium garnet (YbGaG) have been performed between 44-600 mK for the specific heat measurements and from 70 mK up to 4.2K for the magnetisation and susceptibility measurements. Specific heat measurements indicate that the magnetic ordering takes place in two steps. Initially there exists a magnetic ordering of unknown nature represented by a large broad hump with a rounded maximum. At about 180 mK, and below 54 mK, a long-range magnetic ordering occurs evidenced by a lambda-type anomaly in the specific heat. The changes in entropy, together with the temperature and field dependence of magnetisation, indicate that the ground state is a well isolated Kramers doublet. Therefore a molecular-field model of dipolar interactions cannot explain the unusual magnetic behaviour of YbGaG.