Magnetization of the compound LaFe11.4Si1.6 with the cubic NaZn13-type structure was measured as functions of temperature and magnetic field around its Curie temperature TC of ∼208 K. It is found that the magnetic phase transition at TC is completely reversible. Magnetic entropy change ΔS, allowing one to estimate the magnetocaloric effect, was determined based on the thermodynamic Maxwell relation. The achieved magnitude of |ΔS| reaches 19.4 J/kg K under a field of 5 T, which exceeds that of most other materials involving a reversible magnetic transition in the corresponding temperature range. The large entropy change is ascribed to the sharp change of magnetization, which is caused by a large negative lattice expansion at the TC. An asymmetrical broadening of |ΔS| peak with increasing field was observed, which is resulted from the field-induced itinerant-electron metamagnetic transition from the paramagnetic to ferromagnetic state above the TC.
Magnetic refrigeration based on the magnetocaloric effect (MCE) of materials is a potential technique that has prominet advantages over the currently used gas compression-expansion technique in the sense of its high efficiency and environment friendship. In this article, our recent progress in explorating effective MCE materials is reviewed with the emphasis on the MCE in the LaFe 13-x Si x -based alloys with a first order magnetic transition discovered by us. These alloys show large entropy changes in a wide temperature range near room temperature. Effects of magnetic rare-earth doping, interstitial atom, and high pressure on the MCE have been systematically studied. Special issues such as appropriate approaches to determining the MCE associated with the first-order magnetic transition, the depression of magnetic and thermal hystereses, and the key factors determining the magnetic exchange in alloys of this kind are discussed. The applicability of the giant MCE materials to the magnetic refrigeration near ambient temperature is evaluated. A brief review of other materials with significant MCE is also presented in the article.
Magnetic skyrmions are topologically protected vortex-like nanometric spin textures that have recently received growingly attention for their potential applications in future highperformance spintronic devices. Such unique mangetic naondomains have been recently discovered in bulk chiral magnetic materials, such as MnSi [1][2][3][4] , FeGe [5,6] , FeCoSi [7] , Cu 2 OSeO 3 [8][9][10] , -Mn-type Co-Zn-Mn [11] , and also GaV 4 S 8[12] a polar magnet. The crystal structure of these materials is cubic and lack of centrosymmetry, leading to the existence of Dzyaloshinskii-Moriya (DM) interactions. Unlike the conventional spin configurations, such as helical or conical, that are usually found in chiral magnets, a magnetic skyrmion has a particle-like swirling-spin configuration characterized by a topological index called the skyrmion number [13,14] . The nontrivial topology of magnetic skyrmions results in a number of
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