Doping the intermetallic compound ErNi3Al9 with Cu: A structural and magnetic characterization of a phase transition

Abstract In this work, the effect of Cu-doping on the structural and magnetic properties of the ErNi 3 Al 9 compound is reported. X-ray diffraction (XRD) and magnetization experiments as a function of temperature and applied magnetic field have been performed on Er(Ni 1− x Cu x ) 3+ y Al 9− y ( x  = 0.0, 0.1, 0.8, 0.9, 1.0 and y  = 0 or 1) intermetallic compounds. XRD analysis shows that the substitution of Ni by Cu in ErNi 3 Al 9 changes the crystal symmetry from trigonal R 32 to tetragonal I 4/ mmm , even though a clear transition region cannot be established due to the presence of secondary metal phases for intermediate Ni-Cu concentrations. The T -dependence of the magnetic susceptibility shows that the transition temperatures across the series are unaffected by the doping. Moreover, the anisotropic magnetic responses of the MvsT curves measured in the ab -plane and along the c -axis for the series end members may be indicative of strong crystalline electric field (CEF) effects. In fact, we suggest a crystal electric field (CEF)-driven effect due to the different point symmetries for those members. By applying an anisotropic spin model we are able to extract the crystal field parameters, reproduce the macroscopic data and compare these to the previously reported experimental values for ErCu 4 Al 8 . Finally, our set of data show clearly that the phase transition is more evident in the X-ray and crystal field effects than in the T -dependent magnetization.