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We investigate the magnetic and magnetocaloric properties of the new Mn4-xFexGa2Sn compounds (x = 0, 0.1, 0.4, 0.6, and 0.8) from DC magnetization measurements. These phases crystallize in a lacunar form of the η-Fe2-xGe type of structure (P63/mmc). They present a second- order paramagnetic to ferromagnetic transition whose temperature increases upon increasing the Fe content from TC = 317 K for x = 0 up to TC = 411 K for x = 0.8. The alloys with x ≤ 0.4 further exhibit another transition at lower temperature associated with a spin reorientation. The maximal magnetization and magnetic entropy change are found almost constant throughout the series close to ~7.4 µB/f.u. and ~12 mJ cm-3 K-1 (for µ0ΔH = 2.4 T), respectively. The magnetocaloric properties of Mn4-xFexGa2Sn are compared with those of previously investigated materials with high- temperature magnetic transition and their potential interest for high-temperature magnetocaloric applications is briefly discussed. [ABSTRACT FROM AUTHOR]

We report on the kinetics of hydrogen absorption and desorption in magnetocaloric La(Fe,Si)13 materials based on experimental results and model calculations. In the model, the diffusion process is considered to take place dominantly in a hydriding or dehydriding reaction. An important parameter "characteristic absorption/desorption time" is introduced to predict the kinetics of hydriding/dehydriding reaction in a simple way. The application of the model on the La0.9Ce0.1Fe11.44Si1.56 compound gives coincident kinetic results with those determined from experiments. It indicates that the model provides an efficient guidance for measuring and comparing the kinetic property of the magnetocaloric La(Fe,Si)13Hy materials. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of LaFe11.6Si1.4/Ce40Co60 bulk composites prepared by hot pressing sintering (HPS), followed by high-temperature diffusion annealing, were investigated. During the HPS process, the La(Fe,Si)13 alloy powder particles combined with Ce40Co60 binder and a porous structure with high mechanical strength were obtained. The addition of Ce40Co60 can also promote the peritectic reaction. Annealing has important effects on the magnetocaloric properties due to the diffusion of Ce and Co into the La(Fe,Si)13 phase during annealing. HPS samples were annealed at 1373 K for 24 h, and a table-like magnetocaloric effect, exhibiting a constant high magnetic entropy change (− ∆SM) of ~ 4.0 J/(kg K) in a commercially useful temperature region of 28 K (236–264 K), was obtained for a field change of 2 T. The values of full width at half maximum of (− ∆SM)–T plots (ΔTFWHM) and enhanced refrigeration capacity for the composites are 55 K and 173 J/kg, respectively, for a field change of 2 T. The composites exhibit high compressive strength of up to 312 MPa. The present results indicate that LaFe11.6Si1.4/Ce40Co60 bulk composites can meet the requirement of near room temperature magnetic refrigeration based on the Ericsson cycle. [ABSTRACT FROM AUTHOR]

In this paper, we report on the magnetic properties and magnetocaloric effect (MCE) in NaZn13-type LaFe11.2Co0.7Si1.1Cx (x=0.1 and 0.3) close to room temperature. The Landau theory as well as the temperature dependence of magnetization data revealed that LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3 exhibit a second-order magnetic transition near their Curie temperature. We have calculated the magnetocaloric effect both in terms of isothermal entropy change and adiabatic temperature change using the magnetization and the direct measurements. Under an external field change from 0 to 5 T, -ΔS is 14.5 J/kg K (TC=290 K) and 8 J/kg K (TC=310 K) for x=0.1 and 0.3, respectively. The calculated refrigerant capacity for a field change in 0-5 T is about 305 and 286 J/kg K, for LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3respectively, which is larger than that of some magnetocaloric materials with a first-order phase transition (Gd5Ge2Si2). ΔTad decreases with increasing C content. It was found to be about 1.5 for x=0.1 and 1.2 for x=0.3 under 1.48 T. [ABSTRACT FROM AUTHOR]

The microstructure and magnetocaloric effect of the La0.8Ce0.2(Fe0.95Co0.05)11.8Si1.2 strip-cast flakes annealed between 1273K and 1423K for different time have been investigated. For the flakes annealed for 2h from 1273K to 1423K, the shape and distribution of α-Fe, La-rich and NaZn13-type 1:13 phases are quite sensitive to the annealing temperature. Especially, at a high annealing temperature of 1423K, the 1:13 phase began to decompose into macroscopic α-Fe conglomerations and La-rich dendrites. With the increase of annealing time from 0 to 12h at 1323K, the amount of 1:13 phase increased significantly and reached ∼93.50 wt.% at 12h. However, an overlong annealing time also led to 1:13 phase decomposition and influenced the magnetic performance. For the flakes annealed at 1323K for 12h, large magnetic entropy change value of 18.12Jkg-1K-1 at 5T has been obtained. The present results indicate that strip casting method can potentially be used in mass production of high performance magnetocaloric materials. [ABSTRACT FROM AUTHOR]