Seminar of International Laboratory of High Magnetic Fields and Low Temperatures PAS
ul. Gajowicka 95, sala seminaryjna (nowy budynek, II piętro)
Magnetic and magnetocaloric properties of MnFe(P,Si,B) materials B2
F. Guillou
FAME, Delft University of Technology, Mekelweg, The Netherlands
The magnetocaloric effect (MCE) is the temperature change of a magnetic material due to a magnetic field change. Involving this effect into a thermodynamic cycle could lead to a broad range of applications. Currently, one of the most attractive is the magnetic refrigeration at room temperature. This magnetic cooling offers the possibility to advantageously replace the conventional vapour compression technology since it has a higher efficiency and it does not use refrigerant gases which are greenhouse gases. The search for magnetocaloric materials displaying large performances paves the way for the development of this technique.
Since more than one decade, a special interest is paid on materials presenting a so called “Giant-MCE” around a first order magnetic transition. Among the various candidates, the manganese alloys MnFe(P,X) presenting a Fe2P-type structure are most promising (based on 3d elements, Curie temperature around room temperature, mechanical stability...). In this family, one of the latest developments has been achieved by the substitution of phosphorous by boron, an element suitable to control the strength of the first order ferromagnetic transition while keeping the saturation magnetization unmodified [1]. Thanks to this “miraculous” effect of B, the MnFe(P,Si,B) materials have been designed to present a large magnetocaloric effect at intermediate magnetic fields (achievable by permanent magnets). Their structural, magnetic and magnetocaloric properties will be briefly presented. At the end, part of the scientific questions that might be answered by high magnetic field measurements at Wroclaw will be introduced.
1. F. Guillou, G. Porcari, H. Yibole, N van Dijk, E. Brück, Advanced Materials 26, 2671 (2014).
