Recent discoveries of long-range magnetic order in Tsai-type quasicrystals and approximant crystals (ACs) have, for the first time, enabled systematic evaluation of the magnetocaloric effect (MCE) in these hypermaterials. With magnetic transitions now clearly identifiable, pioneering works are revealing magnetocaloric responses unique to hypermaterials. This review summarizes recent progress, focusing on Tsai-type ACs, and highlights that the electron-per-atom (e/a) ratio is the central tuning parameter governing both the magnetic ground state and the resulting MCE, which offers an unconventional MCE control method. Notably, tuning the system toward a magnetic phase boundary yields MCE values comparable to conventional materials promising for low-temperature applications. Furthermore, the recently proposed double hetero-valent elemental substitution expands the compositional stability range of hypermaterials, thereby enabling broader e/a tuning and enhanced MCE in newly synthesized compounds. These advances demonstrate that hypermaterials—including potentially quasicrystals—constitute a promising platform for future exploration of cryogenic magnetocaloric materials.
Yamamoto et al. (Fri,) studied this question.