Discovery of spin glass behavior in Ln 2Fe 4Sb 5 (Ln = La-Nd and Sm)
Single crystals of Ln 2Fe 4Sb 5 (Ln = La-Nd and Sm) were grown from an inert Bi flux. Measurements of the single crystal X-ray diffraction revealed that these compounds crystallize in the tetragonal space group I4/mmm with lattice parameters of a ≈ 4 Å, c ≈ 26 Å, V ≈ 500 Å 3, and Z = 2. This crystal structure consists of alternating LnSb 8 square antiprisms and Fe-sublattices composed of nearly equilateral triangles of bonded Fe atoms. These compounds are metallic and display spin glass behavior, which originates from the magnetic interactions within the Fe-sublattice. Specific heat measurements are void of any sharp features that can be interpreted as contributions from phase transitions as is typical for spin glass systems. A large, approximately linear in temperature, contribution to the specific heat of La 2Fe 4Sb 5 is observed at low temperatures that we interpret as having a magnetic origin. Herein, we report the synthesis, structure, and physical properties of Ln 2Fe 4Sb 5 (Ln = La-Nd and Sm). © 2012 American Chemical Society.