Hydrogenation of the intermediate valence ternary stannides CeRhSn and CeIrSn

Abstract

CeRhSn and CeIrSn were synthesized from the elements via arc-melting. A single crystal from the CeIrSn sample was investigated on the basis of X-ray diffractometer data: ZrNiAl type, P 2 m , a = 743.8 ( 2 ) , c = 407.58 ( 7 ) pm , w R 2 = 0.0308 , 352 F 2 values and 14 variable parameters. An important structural feature of CeIrSn are relatively short Ce Ir distances ( 4 × 303 and 1 × 308 pm ). Hydrogenation of these ternary stannides leads to the formation of the new hydrides CeRhSnH 0.8 and CeIrSnH 0.7 which adopt the same crystal symmetry as the original compounds but a larger unit cell volume after hydrogen insertion. Magnetization, electrical resistivity and thermoelectric power measurements reveal a change of the ground state of the cerium from intermediate valence to the nearly trivalent state induced by hydrogenation. Moreover, 119Sn Mössbauer spectroscopic data of CeRhSn, CeIrSn and their hydrides at 4.2 and 78 K indicate only one tin site. The isomer shifts are slightly larger for the hydrogenated samples suggesting a slightly higher s electron density at the tin nuclei of the hydrides.