Revelation of spin glass behavior in Ru doped MnNiGe: experiment and theory.

We report on the nature of the magnetism in Ru substituted MnNiGe using the combined results of x-ray diffraction, dc-magnetization, ac-susceptibility and ab initio calculations. Mn _0.7 Ru _0.3 NiGe crystallizes in Ni ₂ In-type hexagonal structure (P6 ₃ /mmc) at room temperature with lattice parameters a  =  b  =  4.099 [Formula: see text] and c  =  5.367 [Formula: see text]. From the dc-magnetization; a broad peak around 46.55 K, separation between zero-field cooled and field-cooled warming state and non-saturating isothermal magnetization with typical S-type hysteresis indicate glassy behavior. A cusp in [Formula: see text] is observed to shift toward high temperatures with increasing frequency. Mydosh parameter ([Formula: see text]), single-relaxation time ([Formula: see text] s) obtained through critical slowing-down analysis, [Formula: see text] from the Vogel-Fulcher law and Tholence criterion [Formula: see text], confirm that Mn _0.7 Ru _0.3 NiGe belongs to the short-range interaction spin-glass systems with strong coupling between the magnetic clusters. LSDA+U calculations confirmed the competing exchange interactions between large magnetic moments of the Mn ions in Mn _0.7 Ru _0.3 NiGe compound resulting in the formation of spin-glassy characteristics.