  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
LaFe13-xSix-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.
