The magnetocaloric effect of superfine magnets

  • V. V. Korolev
  • I. M. Arefyev
  • A. G. Ramazanova


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.


ferrites hematite maghemite magnetite magnetocaloric effect microcalorimeter second-order phase transition 


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Copyright information

© Springer Science+Business Media, LLC. 2008

Authors and Affiliations

  • V. V. Korolev
    • 1
  • I. M. Arefyev
    • 1
  • A. G. Ramazanova
    • 1
  1. 1.Institute of Solution Chemistry of RASIvanovoRussia

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