X-Message-Number: 18326 From: "Jan Coetzee" <> Subject: magnetic refrigerants Date: Wed, 9 Jan 2002 21:18:48 -0500 This is a multi-part message in MIME format. ------=_NextPart_000_0018_01C19953.3A9BAA20 Content-Type: text/plain; charset="iso-8859-1" Transition-metal-based magnetic refrigerants for room-temperature applications O. TEGUS, E. BR CK, K. H. J. BUSCHOW & F. R. DE BOER Van der Waals-Zeeman Instituut, Universiteit van Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam, The Netherlands Correspondence and requests for materials should be addressed to E.B. (e-mail: ). Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) have recently been demonstrated as a promising alternative to conventional vapour-cycle refrigeration. In a material displaying the MCE, the alignment of randomly oriented magnetic moments by an external magnetic field results in heating. This heat can then be removed from the MCE material to the ambient atmosphere by heat transfer. If the magnetic field is subsequently turned off, the magnetic moments randomize again, which leads to cooling of the material below the ambient temperature. Here we report the discovery of a large magnetic entropy change in MnFeP0.45As0.55, a material that has a Curie temperature of about 300 K and which allows magnetic refrigeration at room temperature. The magnetic entropy changes reach values of 14.5 J K-1 kg-1 and 18 J K-1 kg-1 for field changes of 2 T and 5 T, respectively. The so-called giant-MCE material Gd5Ge2Si2 (ref. 2) displays similar entropy changes, but can only be used below room temperature. The refrigerant capacity of our material is also significantly greater than that of Gd (ref. 3). The large entropy change is attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field. ------=_NextPart_000_0018_01C19953.3A9BAA20 Content-Type: text/html; [ AUTOMATICALLY SKIPPING HTML ENCODING! ] Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=18326