Giant Magnetostriction in Ferrimagnetic SmFe ₅ As ₃

Magnetostrictive materials are of interest not only from a fundamental perspective but also for their potential applications, spanning spintronics to energy harvesting. A new magnetostrictive material—SmFe 5 As 3 —reveals a complex interplay between magnetostriction, magnetic properties, and the crystal structure behavior. The ground state of SmFe 5 As 3 is ferrimagnetic, as evidenced by magnetic susceptibility data, band‐structure calculations, and XANES measurements. At K, part of the Fe sublattice reorients, transitioning into a ferromagnetic state. This is followed by an entrance into the paramagnetic state at K. The effects observed in the magnetic measurements are accompanied by structural phase transitions. All three phases—below , between and , and above —are described by the same structural motif of the UCr 5 P 3 type (monoclinic space group ), differing only in the degree of deformation of the Fe–As framework. The new material exhibits giant magnetostriction of . Dilatometry measurements on a SmFe 5 As 3 single crystal indicate strongly diverse behavior, exhibiting not only negative, but also zero, as well as positive thermo‐elastic effects.