Abstract
The magnetocaloric effect (MCE) of aqua suspensions based on superfine magnetite (Fe3O4), hematite (α-Fe2O3), maghemite (γ-Fe2O3), samarium ferrite (SmFe2O4) and gadolinium ferrite (GdFe2O4) as well as of magnetite-based ferrofluids was calorimetrically determined in the range of the temperatures from 283 to 253 K. MCE has a positive magnitude for all investigated systems except a hematite-based system. For the suspensions on the basis of MCE temperature dependence it was determined that superfine magnetite transformed into α-Fe2O3 at the temperature above 328 K in contrast to monocrystal magnetite. For aqua suspensions of samarium ferrite and gadolinium ferrite and magnetite-based ferrofluids MCE temperature dependence has an extreme behavior which is connected with a second-order phase transition. For the first time it is established that the magnetocaloric effect (MCE) is greatly increased when the magnet is a nanosized material.
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V. V. Korolev, A. E. Zavadskii, V. I. Yashkova, O. V. Balmasova, K. N. Zheleznov and A. G. Ramazanova, Dokl. Akad. Nauk., 361 (1998) 362.
E. P. Kotov and M. I. Rudenko, Tapes and Disks in devices for magnetic recording, Moscow 1986, p. 224 (in Russian).
L. A. Shmeleva, L. N. Savina, N. I. Dyupovkin and V. V. Korolev, Izv. Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol., 38 (1995) 71.
A. E. Zavadskii, V. V. Korolev, V. I. Yashkova, A. G. Ramazanova and V. A. Kobenin, Izv. Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol., 43 (2000) 124.
V. V. Korolev, A. S. Romanov and I. M. Arefyev, Zh. Fiz. Khim., 80 (2006) 380.
S. Tikadzumi, Physics of Ferromagnetism. Magnetic properties of substances, Moscow 1983, p. 304 (in Russian).
V. P. Krasovskii and I. G. Fakidov, Zh. Eksp. Teor. Fiz., 39 (1960) 228.
S. A. Nikitin, U. V. Talalaeva and L. A. Chernikova, Zh. Eksp. Teor. Fiz., 65 (1973) 2058.
S. A. Nikitin, A. S. Andreenko and U. V. Talalaeva, Zn. Eksp. Teor. Fiz., 73 (1977) 228.
S. A. Nikitin, U. V. Talalaeva and A. S. Andreenko, Zh. Eksp. Teor. Fiz., 74 (1978) 205.
K. P. Belov and S. A. Nikitin, Magnetic Properties of Crystalline and Amorphous Media, Nauka, Novosibirsk 1989, p. 400 (in Russian).
K. P. Belov, Usp. Fiz. Nauk., 164 (1994) 603.
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Korolev, V.V., Arefyev, I.M. & Ramazanova, A.G. The magnetocaloric effect of superfine magnets. J Therm Anal Calorim 92, 691–695 (2008). https://doi.org/10.1007/s10973-008-9018-y
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DOI: https://doi.org/10.1007/s10973-008-9018-y