Magnetic ordering of the mixed-spin chain nickelate (Er0.25Gd0.75)2BaNiO5: Spectroscopic study

The interchain interaction and magnetic structure of the (Er0.25Gd0.75)2BaNiO5 single crystal is studied by optical spectroscopy. The magnetic ordering temperature TN=52±1K of this compound with two different rare earths interconnecting nickel chains is well described by a mean-field model. The magnetic moments order along the direction of the nickel chains which is imposed by Er3+ single-ion anisotropy. Fine structure of Er3+ spectral lines was observed and explained by lattice distortions due to disorder in the rare-earth subsystem of the mixed compound.