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The structure and magnetic properties of La(Fe1−xMnx)11.4Al1.6 (0≤x≤0.25) compounds have been studied. The NaZn13-type structure is preserved and the lattice parameter increases linearly with increasing the Mn concentration. The magnetic ground state changes from the antiferromagnetic to the spin-glass or the cluster-glass state by the substitution of Mn for Fe. Furthermore, a field-induced transition from cluster glass to ferromagnet is found for the samples with x=0.05 and 0.10.

Magnetism and magnetic entropy changes in LaFe11Al2Cx (x=0.0, 0.2 and 0.5) compounds have been investigated. The Curie temperature TC is conveniently controlled from 200K to room temperature by varying the carbon concentration. Large magnetic entropy change is obtained over a wide temperature range due to the high magnetization and the drastic decrease in the magnetization around TC. The large magnetic entropy change in wide temperature range, low cost and the convenience of controlling TC suggest that the LaFe11Al2Cx compounds are promising candidates for magnetic refrigerants in the corresponding temperature range.

Magnetic properties and magnetic entropy change in La (Fe1-xMnx)11.7Si1.3Hy compounds have been investigated. A significant increase of the Curie temperature TC and a small increase of the saturation magnetizations µS have been observed after the introduction of interstitial H, which caused a slight volume expansion. The first-order field-induced itinerant-electron metamagnetic (IEM) transition remains and brings about a large magnetic entropy change around room temperatures for the compounds. The maximal magnetic entropy change is about 23.4, 17.7 and 15.9J/kgK under a magnetic field change from 0 to 5T for x=0.01, 0.02 and 0.03, respectively. Therefore, the compounds appear to be potential candidates for magnetic refrigerants around room temperatures.

The LaFe11.5Si1.5H1.3 interstitial compound has been prepared. Its Curie temperature TC (288 K) has been adjusted to around room temperature and the maximal magnetic entropy change (|?S|~17.0 J?kg-1?K-1 at TC) is larger than that of Gd (|?S|~9.8 J?kg-1?K-1 at TC=293 K) by ~73.5% under a magnetic change from 0 to 5 T. The origin of the large magnetic entropy change is attributed to the first-order field-induced itinerant-electron metamagnetic transition. Moreover, the magnetic hysteresis of LaFe11.5Si1.5H1.3 under the increase and decrease of the field is very small, which is favourable to magnetic refrigeration application. The present study suggests that the LaFe11.5Si1.5H1.3 compound is a promising candidate as a room-temperature magnetic refrigerant.