Magnetothermodynamics of α‐NiSO4·6H2O. I. Heat Capacity, Entropy, Magnetic Moment, and Internal Energy, from 0.4° to 4.2°K, with Fields 0–90 kG along the c Axis

摘要: The heat capacity and magnetic moment of single‐crystal α‐NiSO4·6H2O have been measured over a range about 0.4°—4.2°K in stabilized fields 0–90 kG. field was parallel to the c crystallographic axis 4‐cm‐diam spherical sample. Although saturation not attained even at 90 kG 0.4°K, there essentially no temperature coefficient below 0.7°K any field. approached zero for all except small calculable contribution due nuclear polarization high fields. At it found that nuclear‐spin 0.95°K above general equilibrium. 0.90°K equilibrium quite slow indicating rather rapid increase relaxation time with decreasing temperature. Each series provided zero‐entropy reference, spin. These references agreed precise measurements change on adiabatics joining various isoerstedic series. entropy changes, combination work free energy magnetization, enabled evaluation changes internal enthalpy as function With very minor deviations possible represent data by means three state Schottky functions. two upper states are degenerate 4.74 cm−1 (13.55 cal/mole) ground state. variation each individual levels is given. A detailed description magnetocalorimeter included.