Magnetothermodynamics of Antiferromagnetic, Ferroelectric β-Gd2(MoO4)3. II. Heat Capacity, Entropy, Magnetic Moment of the Electrically Polarized Form from 0.4 to 4.2°K with Fields to 90 kG along the a Crystal Axis

The magnetic moment of a 2.49-cm-diam spherical single crystal of electrically polarized β-Gd2(MoO4)3 has been measured with stabilized fields of 500, 1000, 1500, 2500, 5000, 10 000, 15 000, 25 000, 40 000, 65 000, and 90 000 G, along the a crystal axis, and over the range 0.3–4.2°K. The approach to saturation was measured at about 0.43°K over the range 30–90 kG. The temperature independent susceptibility along the a axis (diamagnetic) was determined as −3.1×10−4 cm3/mole Gd3+ and the limiting saturation value was found to be 38 796 G·cm3/mole Gd3+, corresponding to a ga=1.985. The heat capacity has been measured in fields of 0, 1000, 2500, 5000, 10 000, 15 000, 25 000, 40 000, 65 000, and 90 000 G over a range 0.4–4.2°K. The heat of vaporization of momentum, h/2π, from the essentially saturated state was found to be 23.15 and 16.50 cal/mole at 90 and 65 kG, respectively. This may be compared with the work of this process, gaβH, which was 23.85 and 17.22 cal/mole at these two respective fields. Temperature-field observations on 38 isentropes were used to correlate the entropies along 10 isoerstedic heat capacity series. The entropy zero of the electronic and lattice systems was located at magnetic saturation by means of the heat capacity series at 90 and 65 kG. Smoothed correlated values of the heat capacity, entropy, enthalpy, internal energy, magnetic moment and its isoerstedic temperature coefficient, the differential isothermal magnetic susceptibility, and the isothermal work of magnetization have been tabulated over the range 0–90 kG and 0.4–4.2°K. Comments on the use of carbon thermometers at liquid helium temperatures are included.