LaFeSi13based

LaFeSi13-based compounds are a family of iron-based intermetallics characterized by a NaZn13-type cubic crystal structure. They are typically described by the formula LaFe13−xSix (0 ≤ x ≤ about 1.7) or closely related compositions such as LaFe11.5Si1.5, with silicon partially substituting for iron. The structure features a lanthanum atom in a large cage surrounded by a framework of iron and silicon atoms; various dopants can be added to adjust properties.

These materials exhibit ferromagnetism with a tunable Curie temperature. In many compositions the magnetic transition is first order and couples to a small lattice change, yielding a sizable magnetocaloric effect when subjected to an external magnetic field. By adjusting silicon content and dopants, the peak effect can be tuned to occur near room temperature, making them of particular interest for magnetocaloric refrigeration research.

Tuning and variants: Silicon content controls Tc and the strength of the magnetocaloric response. Hydrogenation to form LaFe13−xSixHy and carbon or other dopants can further shift Tc, sharpen the transition, and influence mechanical properties. Substituting a portion of Fe with Co or Mn is also used to tailor magnetization and transition temperature.

Synthesis and structure: Typical preparation involves arc melting in an inert atmosphere followed by homogenization and annealing to produce a single NaZn13-type phase. Post-synthesis treatments such as hydrogenation or carbon insertion are used to modify properties further.

Applications and research: LaFeSi13-based materials are studied as potential candidates for environmentally friendly magnetic refrigeration and for fundamental investigations of coupled magnetic and structural transitions. Challenges include brittleness, thermal hysteresis, and scalable synthesis.