Low-temperature heat capacities and Verwey transition of magnetite

✍ Scribed by Shigeomi Takai; Yukikuni Akishige; Hitoshi Kawaji; Tooru Atake; Etsuro Sawaguchi

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 217 KB
• Volume: 26
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1994.1143

✦ Synopsis

Heat capacities of stoichiometric magnetite crystals (\left(\mathrm{Fe}{3} \mathrm{O}{4}\right)) were measured by adiabatic calorimetry from (T=13 \mathrm{~K}) to (300 \mathrm{~K}). The Verwey transition was observed as a single sharp anomaly at (T=123.82 \mathrm{~K}) in the heat-capacity curve. The transition molar enthalpy (\Delta_{\mathrm{trs}} H_{\mathrm{m}}) and entropy (\Delta_{\text {ts }} S_{\mathrm{m}}) including the tail portion extending from about (T=80 \mathrm{~K}) to (230 \mathrm{~K}) were estimated as (980.8 \mathrm{~J} \cdot \mathrm{mol}^{-1}) and (7.67 \mathrm{~J} \cdot \mathrm{K}^{-1} \cdot \mathrm{mol}^{-1}), respectively. The thermodynamic properties of the transition are discussed. Several thermodynamic functions were calculated from the measured heat capacities and tabulated at round temperatures.