Giant Magnetostriction in Ferrimagnetic SmFe₅As₃

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-SmFe₅As₃-reveals a complex interplay between magnetostriction, magnetic properties, and the crystal structure behavior. The ground state of SmFe₅As₃ is ferrimagnetic, as evidenced by magnetic susceptibility data, band-structure calculations, and XANES measurements. At $T_{m1}=28\pm 4$ K, part of the Fe sublattice reorients, transitioning into a ferromagnetic state. This is followed by an entrance into the paramagnetic state at $T_{m2}=76\pm 4$ K. The effects observed in the magnetic measurements are accompanied by structural phase transitions. All three phases-below $T_{m1}$ , between $T_{m1}$ and $T_{m2}$ , and above $T_{m2}$ -are described by the same structural motif of the UCr₅P₃ type (monoclinic space group $P{2}_1/m$ ), differing only in the degree of deformation of the Fe-As framework. The new material exhibits giant magnetostriction of $2500\times {10}^{-6}$ . Dilatometry measurements on a SmFe₅As₃ single crystal indicate strongly diverse behavior, exhibiting not only negative, but also zero, as well as positive thermo-elastic effects.