Magnetothermodynamics of Nd(C2H5SO4)3⋅9H2O. I. Heat capacity, entropy, magnetic moment from 0.5 to 4.2 °K with fields to 90 kG along the c crystal axis

Abstract

The heat capacity of a 3.920 cm diam spherical single crystal of neodymium ethyl sulfate hydrate has been measured with stabilized fields of 0, 1000, 2500, 5000, 10 000, 15 000, 25 000, 40 000, 65 000, and 90 000 G along the c crystal axis, from 0.5 to 4.2 °K. The zero of electronic entropy was reached at 90, 65, and 40 kG and the lower temperatures. Corrections were applied for the nuclear polarization of the protons and the neodymium isotopes 143 and 145. The isoerstedic entropy changes derived from the heat capacity series were interconnected by 29 series of temperatures on ’’adiabatics,’’ corrected to isentropes. The lattice heat capacity in the liquid helium range can be represented by Clat= (1.44±0.01) ×10−3 T3 gibbs/mole NES. The magnetic moment was measured over the same field and temperature ranges used for the heat capacities plus magnetic moments at 500 and 1500 G. The saturation limit of the temperature-dependent magnetic system was 10 036 G⋅cm3/mole NES, corresponding to gc=3.594. A temperature-independent magnetic susceptibility was found to be 0.00341 cm3/mole NES. Smoothed correlated values of the heat capacity, entropy, enthalpy, internal energy, magnetic moment and its isoerstedic temperature coefficient, differential isothermal magnetic susceptibility, and the isothermal work of magnetization have been tabulated over the range 0–90 kG and 0.5–4.2 °K. These data will be used as a starting reference for investigating the properties of NES in the region below 0.5 °K. Comparison of the magnetic moment and heat capacity data with an ionic crystal field model plus a dipolar molecular field, using derived parameters, leads to general good agreement.