Complex rare-earth tetrelides, RE5(SixGe1-x)(4): New materials for magnetic refrigeration and a superb playground for solid state chemistry

摘要

A ``giant magnetocaloric effect'' discovered in 1997 for Gd5Si2Ge2 near room temperature has triggered optimism that environmentally-friendly, solid-state magnetic refrigeration may be viable to replace gas-compression technology in the near future. Gd5Si2Ge2 is one member of an extensive series of rare-earth compounds, RE5( SixGe1-x)(4). Due to the complexity of their structures and flexibility associated with chemical compositions, this series is an attractive ``playground'' to study the interrelationships among composition, structure, physical properties and chemical bonding. This tutorial review, which is directed toward students and researchers interested in structure-property relationships in solids, summarizes recent efforts concerning the synthesis, structure, physical properties, chemical bonding and chemical modifications of RE5( SixGe1-x)(4). A brief history of refrigerants, to present certain motivating factors for this research effort, as well as a brief overview of the magnetocaloric effect serves to introduce this review.