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OnderzoekVan Swinderen Institute

Prof. dr. E. Brück, Faculty of Applied Sciences, Delft University of Technology: Mixed Magnetism for refrigeration

Roster

WhenWhere
11 October 2012 FWN-Building 5111.0080, Nijenborgh 4, 9747 AG, Groningen
Speaker: Prof. dr. Ekkes Brück
Affiliation: Faculty of Applied Sciences, Delft University of Technology
Title: Mixed Magnetism for refrigeration
Date: 11-10-2012
Start: 16.00 (Doors open and coffee available at 15.30)
Location: FWN-Building 5111.0080
Host: Thom Palstra

Abstract

Modern society relies on readily available refrigeration. Magnetic refrigeration has three prominent advantages compared to compressor-based refrigeration. First there are no harmful gasses involved, second it may be built more compact as the working material is a solid and third magnetic refrigerators generate much less noise [1]. The efficient coupling between lattice degrees of freedom and spin degrees of freedom in magnetic materials can be used for refrigeration and energy conversion. This coupling is enhanced in materials exhibiting the giant magnetocaloric effect. First principle electronic structure calculations on hexagonal MnFe(P, Si) reveal a new form of magnetism: the coexistence of strong and weak magnetism in alternate atomic layers. The weak magnetism of Fe layers (disappearance of local magnetic moments at the Curie temperature) is responsible for a strong coupling with the crystal lattice while the strong magnetism in adjacent Mn-layers ensures Curie temperatures high enough to enable operation at and above room temperature [2]. Varying the composition on these magnetic sublattices gives a handle to tune the working temperature and to achieve a strong reduction of the undesired thermal hysteresis. In this way we design novel materials based on abundantly available elements with properties matched to the requirements of an efficient refrigeration or energy-conversion cycle.

[1] Brück E., J. Phys. D-Appl. Phys. 38(2005) R381-R391 [2] Dung NH, Ou ZQ, Caron L, Zhang L, Thanh DTC, de Wijs GA, de Groot RA, Buschow KHJ, Brück E. Adv. Energy Mat. 2011;1:1215.

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Last modified:12 September 2014 11.21 a.m.