Magnetothermodynamics of Ce2Zn3(NO3)12 · 24H2O. I. Heat capacity, entropy, magnetic moment from 0.5 to 4.2 °K with fields to 90 kG along the a crystal axis

Abstract

The magnetic moment and heat capacity of a 4.059 cm diam. spherical single crystal of cerium zinc nitrate hydrate (CZN) 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 a crystal axis, from 0.5 to 4.2°K. The zero of electronic entropy was reached at fields of 90, 65, and 40 kG and the lower temperatures. The isoerstedic entropy changes derived from heat capacity series were interconnected by 28 series of temperatures vs fields on isentropes. Analysis of the heat capacity data established that the first excited doublet is (61.0±0.3+7.8×10−10H2) cal/mole (h/2π) above the zero field ground state. H is in gauss. The splitting factor of the ground state doublet was evaluated calorimetrically as gH=1.8175−7.88×10−12H2G −2. Near 0.5°K, and over the range 40–90 kG, the total magnetic moment reaches temperature-independent limits at each field. Subtracting the low temperature limiting value of the temperature-dependent moment, 5075–6.60×10−8 H2G · cm3/mole Ce3+, from the total, enabled the evaluation of the differential temperature-independent susceptibility as 2.632×10−2−7.8×10−14H2 cm3/mole Ce3+. Thus, Mlimit T→0 = (5075+2.632×10−2 H−6.60×10−8H2−2.6×10−14H 3) G · cm3/mole Ce3+, where H is in gauss. 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. The problem of obtaining crystals of CZN which approximate stoichiometric proportions has been discussed. The principal purpose of the data is to lay a foundation for subsequent measurements needed to establish a temperature scale for CZN to the millidegree region.