The La(Fe,Mn,Si)₁₃H_z magnetic phase transition under pressure

Abstract

We study the magnetocaloric metamagnetic transition in LaFe11.74Mn0.06Si1.20 and LaFe11.76Mn0.06Si1.18H1.65 under hydrostatic pressure up to 1.2 GPa. For both compounds, hydrostatic pressure depresses the zero field critical temperature. However, in detail, pressure influences the magnetic properties in different ways in the two compounds. In the dehydrogenated case the transition broadens under pressure whereas in the hydrogenated case the transition sharpens. In both cases thermal hysteresis increases under pressure, although with different trends. These observations suggest both intrinsic and extrinsic hysteresis loss brought about by the use of hydrostatic pressure. We explore the multicaloric field‐pressure cycle, demonstrating that although the gain introduced by overcoming the magnetic hysteresis loss is closely countered by the loss introduced in the pressure cycle, there are significant advantages in that the temperature range of operation can be finely tuned and extended, and the magnetocaloric transition can operate in lower absolute applied fields (<0.5 T), potentially overcoming one of the most significant bottlenecks to the commercialization of this technology.

Fine control of Curie temperature of magnetocaloric alloys La(Fe,Co,Si)13 using electrolytic hydriding

“…La(Fe,Si)13 with Co substitutionally doped on to the Fe sites (with TC control of the order of 2 K) [11,12,24] produces a second order broad transition at high Co concentration with impaired ΔS and ΔTad performance compared to the base material [11,12], and more accurate targeting of TC near RT is difficult due to very reliable variations in Co content of the order of 1% required. This is similarly the case for Mn doping followed by full hydrogenation (a first-order transition) [17,[25][26][27]. However, a significant advantage in having a broad transition is that it offers a greater effective operation temperature range per composition, relaxing the stringency on the step size of TC in a cascaded set to perhaps 3 K. Nevertheless, accurate and reliable targeting of any compound's TC is a strong advantage for future scale-up of MCE refrigerant production.…”

Multicalorics --- new materials for energy and straintronics (R e v i e w)

“…Other promising " natural" multicalorics with I order phase transitions are alloys based on La−Fe−Si with a " giant" MCE. Thus, for instance, an alloy of hydrogenated La−Fe−Si with " giant" values of BCE and MCE was suggested for the multicaloric cooling concept [43]. The multicaloric approach can be also implemented using ferroelectric materials with a " giant" ECE in the region of a structural phase transition.…”

Multicaloric materials and effects

“…The energy dissipated during the multicaloric cycle shown (red dashed line) is given to a good approximation by |∆p∆v|, where ∆p = p2 -p1 and ∆v is the difference in specific volumes for the two phases (Figure 4b) 23 . Experimentally, these kind of multicaloric cycles have been realized using Fe-Rh 23 and La-Fe-Mn-Si 32 .…”