Effects of carbon on magnetic properties and magnetic entropy change of the LaFe11.5Si1.5 compound

Abstract

Effects of the interstitial carbon atoms on the magnetic properties, especially on the magnetic entropy change, of the LaFe11.5Si1.5 compound, have been studied. X-ray diffraction patterns reveal a monotonous increase of the lattice constant with the concentration of carbon, while the cubic NaZn13-type structure remains unchanged. The Curie temperatures TC of LaFe11.5Si1.5Cy are ∼195, 225, and 241 K for y=0, 0.2, and 0.5, respectively, increasing with the increase of carbon concentration. The maximal magnetic entropy changes |ΔS| of LaFe11.5Si1.5Cy at the respective TC under a magnetic field change of 0–5 T are ∼24.6, ∼22.8, and ∼12.7 J/kg K for y=0, 0.2, and 0.5, respectively, notably exceeding that of Gd (|ΔS| ∼9.8 J/kg K at TC=293 K). The |ΔS| of LaFe11.5Si1.5C0.2 is nearly as giant as that of the parent alloy LaFe11.5Si1.5 due to the first-order field-induced itinerant-electron metamagnetic transition that occurs in both compounds clearly observed for the LaFe11.5Si1.5C0.5 compound. With the increase of carbon concentration, the nature of magnetic transition has been changed from first order to second order, which results in the significant decrease of the magnetic entropy change. The large |ΔS|, convenient adjustment of TC and relatively low cost make the LaFe11.5Si1.5Cy interstitial compounds promising candidates for magnetic refrigerants in the corresponding temperature range.

Recent Progress in Exploring Magnetocaloric Materials

“…The decrease of |S| for x > 0.4 could be due to impurity phase, which broadens the phase transition. A slightly different carbides LaFe 11.5 Si 1.5 C δ was also studied, [51] and similar effects were observed.…”

“…Our study showed that the entropy change ΔS of Ni 51 The ΔS shows a table-like peak under 5T for Ni 51 Mn 49-x In x . The flat plateau of ΔS should reflect the intrinsic nature of magnetocaloric effect.…”

“…It is therefore necessary to obtain chemically stable interstitial compounds with high T C s and great |S| values. Chen et al [50,51] studied the effects of interstitial carbon for the lattice expansion. [52] The Curie temperatures grows from 195 K for δ=0 to 250 K for δ=0.6.…”

Peritectic Solidification Path of the La(Fe,Si)13 Phase in Dual-Phase Directionally Solidified La-Fe-Si Magnetocaloric Alloys

“…[1][2][3] In this case, La-Fe-Si alloy, with NaZn 13 -type La(Fe,Si) 13 phase, has been reported as a promising candidate for magnetic refrigerants. [4,5] La(Fe,Si) 13 alloy exhibits a giant magnetocaloric effect (MCE, which refers to the heating or cooling of magnetic materials due to a varying magnetic field) due to a magnetic field-induced, first-order itinerant electron metamagnetic (IEM) transition above the Curie temperature (T C ). [6] La(Fe,Si) 13 alloy displays a small hysteresis and an isotropic magnetovolume effect accompanied by the phase transition.…”

“…[4,5] La(Fe,Si) 13 alloy exhibits a giant magnetocaloric effect (MCE, which refers to the heating or cooling of magnetic materials due to a varying magnetic field) due to a magnetic field-induced, first-order itinerant electron metamagnetic (IEM) transition above the Curie temperature (T C ). [6] La(Fe,Si) 13 alloy displays a small hysteresis and an isotropic magnetovolume effect accompanied by the phase transition. [7][8][9] These properties are beneficial for a cyclic use of La-Fe-Si alloys because of the existing giant magnetocaloric effect.…”