Reduction of hysteresis losses in the magnetic refrigerant Gd5Ge2Si2 by the addition of iron

Abstract

The magnetocaloric effect is the change in temperature of a material as a result of the alignment of its magnetic spins that occurs on exposure to an external magnetic field. The phenomenon forms the basis for magnetic refrigeration, a concept purported to be more efficient and environmentally friendly than conventional refrigeration systems. In 1997, a 'giant' magnetocaloric effect, between 270 K and 300 K, was reported in Gd5Ge2Si2, demonstrating its potential as a near-room-temperature magnetic refrigerant. However, large hysteretic losses (which make magnetic refrigeration less efficient) occur in the same temperature range. Here we report the reduction (by more than 90 per cent) of these hysteretic losses by alloying the compound with a small amount of iron. This has the additional benefit of shifting the magnetic entropy change peak (a measure of the refrigerator's optimal operating temperature) from 275 K to 305 K, and broadening its width. Although the addition of iron does not significantly affect the refrigerant capacity of the material, a greater net capacity is obtained for the iron-containing alloy when the hysteresis losses are accounted for. The iron-containing alloy is thus a much-improved magnetic refrigerant for near-room-temperature applications.

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] .…”

Inverse barocaloric effect in the giant magnetocaloric La–Fe–Si–Co compound

“…Here we report on the barocaloric eff ect of the giant magnetocaloric material LaFe 11.33 Co 0.47 Si 1.2 . La(Fe,Si) 13, and the derived quaternary compounds are considered nowadays to be the most promising working materials for magnetic refrigeration technology 11,12 . Th ey feature relatively large entropy changes with a very low hysteresis and do not contain toxic materials.…”

“…Th ey feature relatively large entropy changes with a very low hysteresis and do not contain toxic materials. Materials with reduced hysteresis are highly desirable because irreversibilites associated with such a hysteresis cause a reduction in the refrigerant capacity 13,14 . LaFe 13 − x Si x compounds are stable with the cubic NaZn 13 structure (space group Fm c 3 ) in a concentration range 1.2 ≤ x ≤ 2.5 (ref.…”

Phase diagram and magnetocaloric effect ofCoMnGe1-xSnxalloys

“…In the case of magnetostructural transitions, a different crystal structure is found on either side of the phase transition, for example in Gd 5 (Si 1−x Ge x ) 4 [1] or in shape memory alloys such as Ni 2+x Mn 1−x Ga [7]. In these cases, hysteresis can be much larger and there have been efforts, via controlled doping, to minimise it [8].…”