LOW-TEMPERATURE HEAT-CAPACITIES AND VERWEY TRANSITION OF MAGNETITE

Heat capacities of stoichiometric magnetite crystals (Fe3O4) were meas ured by adiabatic calorimetry from T = 13 K to 300 K. The Verwey trans ition was observed as a single sharp anomaly at T = 123.82 K in the he at-capacity curve. The transition molar enthalpy Delta(trs)H(m) and en tropy Delta(trs)S(m) including the tail portion extending from about T = 80 K to 230 K were estimated as 980.8 J.mol(-1) and 7.67 J.K-1.mol( -1), respectively. The thermodynamic properties of the transition are discussed. Several thermodynamic functions were calculated from the me asured heat capacities and tabulated at round temperatures.