SrMGe2O6 (M = Mn, Co): a family of pyroxene compounds displaying multiferroicity

Abstract

The family of Sr-based pyroxene compounds SrMGe₂O₆ (M = Mn, Co) has been synthesized and investigated by means of X-ray single crystal and powder diffraction, neutron diffraction, magnetic susceptibility and heat capacity measurements. Both SrMnGe₂O₆ and SrCoGe₂O₆ crystallize with monoclinic C2/c symmetry. Magnetoelectric and neutron powder diffraction measurements indicate that SrMnGe₂O₆ is a multiferroic of spin origin with a magnetic order characterized by a cycloidal spin configuration below 4.5 K, while SrCoGe₂O₆ displays a commensurate magnetic structure below 10 K with space group P_c2₁/c. The comparison between Sr- and Ca-based pyroxenes from structural and magnetic viewpoints allows us to identify the relevant parameters for the magnetic ground states and magnetoelectric properties.