Excellent cryogenic magnetocaloric properties in heavy rare-earth based HRENiGa2 (HRE = Dy, Ho, or Er) compounds

Abstract

RENiX2 compounds, where RE = rare-earth element and X = p-block element, have been highly regarded for cryogenic magnetocaloric applications. Depending on the elements, they can crystallize in CeNiSi2-type, NdNiGa2-type, or MgCuAl2-type crystal structures, showing different types of magnetic ordering and thus affect their magnetic properties. Regarding the magnetocaloric effect, MgCuAl2-type aluminides show larger values than those of the CeNiSi2-type silicides and the NdNiGa2-type gallides due to the favored ferromagnetic ground state. However, RENiGa2 gallides can crystallize in either NdNiGa2- or MgCuAl2-type structures depending on the RE element. In this work, we select heavy RE (HRE) elements for exploring the microstructure, magnetic ordering and magnetocaloric performance of HRENiGa2 (HRE = Dy, Ho or Er) gallides. They all crystallize in the desired MgCuAl2-type crystal structure which undergoes a second-order transition from ferro- to para-magnetic state with increasing temperature. The maximum isothermal entropy change (∣∆Sisomax∣) values are 6.2, 10.4, and 11.4 J kg−1 K−1 (0–5 T) for DyNiGa2, HoNiGa2, and ErNiGa2, respectively, which are comparable to many recently reported cryogenic magnetocaloric materials. Particularly, the excellent magnetocaloric properties of HoNiGa2 and ErNiGa2 compounds, including their composite, fall in the temperature range that enables them for the in-demand hydrogen liquefaction systems.

Structural, magnetic and magnetocaloric properties in distorted RE 2NiTiO6 double perovskite compounds

“…Up to now, a series of MR materials with potential application near ambient temperature have been identified, such as Gd-Si-Ge [6], La-Fe-Si/Al [7], Mn-Fe-P-As/Ge/Si [8,9], and Ni-Mn-X (X = Ga, In and Sn) [10,11], etc. In comparison, rare earth (RE)-based compounds and oxides are regarded as the promising cryogenic MR materials for MR technology on account of their unique advantages and application prospects in the liquefaction of extremely low-temperature resources including helium (He), hydrogen (H 2 ) and nitrogen (N 2 ) [12][13][14][15][16].…”

Rotating magnetocaloric effect in highly anisotropic TbIII and DyIII single molecular magnets

“…Recently reported materials for conventional MCE show the variation of TEC (5) in µ 0 Δ H = 1 T between 1 and 10 J K −1 kg −1 41 , 48 – 53 ; thus, the RMCE results reported for Tb-SMM and Dy-SMM fall in a moderate range with TEC (5) = 2.42 J K −1 kg −1 for the former and TEC (5) = 2.13 J K −1 kg −1 for the latter in the same magnetic field. The studies of the RMCE in HoNiGe 3 single crystal 54 presented a much higher TEC (5) of approximately 12 J K −1 kg −1 in µ 0 Δ H = 5 T compared to the corresponding values of 3.55 J K −1 kg −1 in µ 0 H = 4 T for Tb-SMM , and 2.82 J K −1 kg −1 in µ 0 H = 5 T for Dy-SMM , but with significantly smaller entropy change in µ 0 Δ H = 1 T and higher temperatures for which the entropy change maximum was observed (between 5 and 15 K).…”

Magnetocaloric effect and critical behavior of the La0.75Ca0.1Na0.15MnO3 compound

“…Around the FM-PM, various phase-transition measurable quantities can be determined using a series of critical exponents dening the behavior of these magnetic materials. [4][5][6][7] The design and development of magnetic refrigeration devices require a solid thermodynamic description of the magnetic system, as well as its characteristics during each phase of the refrigeration cycle. Recently the magnetic properties and the magnetocaloric effect (MCE) for La 0.75 Ca 0.1 Na 0.15 MnO 3 (LCNMO) manganite undergoing a second order (SO) FM-PM phase transition, were reported in our previous work.…”