Transition-metal-based magnetic refrigerants for room-temperature applications

Abstract

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.

Multicaloric effect in ferroelectric PbTiO3from first principles

“…Contrary to the old belief that such effects, while common, are miniscule, a large variety of giant caloric effects has been recently discovered in some ferroic materials [1][2][3][4][5][6][7][8][9][10] . These discoveries have opened the door to the use of these giant effects in an efficient and environmentally friendly solid-state refrigeration technology.…”

“…Moreover, given a relative abundance of extrinsic multiferroics among ferroics with multiple order parameters, such prediction may open an unusual route to solid state refrigeration advancement. Recent discoveries of giant caloric effects in some ferroic materials [1][2][3][4][5][6][7][8][9][10] have opened the door to the use of solidstate materials as an alternative to gases for conventional and cryogenic refrigeration 11 . The wide class of ferroics includes such diverse materials as ferromagnets and magnetic materials, ferroelectrics, ferroelastics and multiferroics.…”

Stable magnetostructural coupling with tunable magnetoresponsive effects in hexagonal ferromagnets

“…These magnetoelastic transitions have been utilized in the intensive investigations of a large body of giant magnetocaloric materials [19][20][21][22][23][24][25][26][27] . In contrast, in typical FMMTs, the change of structural symmetries of austenite and martensite is remarkable [6][7][8][9][10][11] .…”

Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe)2 (P,Ge) intermetallic compounds

“…Along with the Arrott plots, very interesting could be a comparison of magnetic entropy change curves. In the high magnetic field of 5 T, the highest entropy change was evaluated for the Mn 1 was even lower i.e. 14 J/(kg·K) at the same magnetic field.…”

“…Interesting properties of MnFe(P 1 − x Y x ) compounds were for the first time reported by Tegus et al [1] in MnFeP 0.45 As 0.55 . In their other paper, the authors have shown an impact of changing P/As ratio on the Curie temperature and magnetic entropy change [2].…”