Magnetothermodynamics of gadolinium gallium garnet. III. Heat capacity, entropy, magnetic moment from 0.5 to 4.2 °K, with fields to 90 kG along the [110] axis

Abstract

The magnetic moment of a 2.44 cm diam spherical single crystal of gadolinium gallium garnet has been measured with stabilized fields of 500, 1000, 2500, 5000, 10 000, 12 500, 15 000, 20 000, 25 000, 40 000, 65 000, and 90 000 G along the [110] crystal axis, over the range 0.5 to 4.2 °K. The magnetic moment reached saturation at 90 kG and 0.35 °K. The heat capacity was measured over the 0.5–4.2 °K temperature range and the above fields except that 500 and 1000 G were omitted and zero field included. The zero of electronic and lattice entropy was located at 90 kG and magnetic saturation. Temperatures were measured versus field on 36 adiabatics, corrected with respect to entropy. These provided multiple intersections with the isoerstedic heat capacity curves, so that the entropy could be evaluated over the entire temperature and field ranges of the investigation. The saturation moment was found to be M_[110] = 38 963 G⋅cm³/mole Gd³⁺, equivalent to g_[110] = 1.993. This may be compared with the previous similar measurements M_[100] = 39 059 and M_[111] = 38 979 G⋅cm³/mole Gd³⁺, corresponding to g_[100] = 1.998 and g_[111] = 1.994. Smoothed correlated values of the heat capacity, entropy, enthalpy, internal energy, magnetic moment and its differential isoerstedic temperature coefficient, differential isothermal magnetic susceptibility, and the isothermal work of magnetization, have been tabulated over the ranges 0–90 kG and 0.5–4.2 °K.