Magnetic properties of UCoAl1-ySiy and UCoAl1-yGey solid solutions

Results of crystal-structure and magnetization studies performed on the UCoAl1-ySiy and UCoAl1-yGey solid solutions with xless than or equal to0.4 are presented. Both, the substitutions of Si and Ge for Al lead to a gradual suppression of metamagnetism by increasing the value of the critical field of the metamagnetic transition (MT) and reducing the magnetization gain at MT. In the case of the Ge substitution the magnetization curves for x>0.06 indicate the possibility of onset of weak ferromagnetism, which may appear at temperatures below 5 K or for higher Ge concentrations, x>0.4. For the corresponding Si concentrations, on the other hand, we have found only further weakening of the paramagnetic signal. The substitution-induced variation of interatomic distances, the 5f-ligand hybridization and the consequent changes of the 5f-electron character are discussed to cause the observed evolution of magnetism in the studied compounds. (C) 2002 Elsevier Science B.V. All rights reserved.