Magnetic and thermodynamic studies on the charge and spin ordering in the highly-doped La2− xSrxCoO4

We report magnetic studies on the charge and spin ordering in La2− xSrxCoO4 for x = 1 / 3 , 0.60, and 0.75. The magnetic susceptibility displays a clear cusp which we attribute to a spin glass freezing transition in all three compositions stduied. The behaviors of the evaluated effective magnetic moment and Curie-Weiss temperature indicate that the antiferromagnetic (AFM) interaction among Co 2 + ions surrounded by the non-magnetic Co 3 + weakens with increasing the doping concentration x. In addition, we have found that the incommensurate AFM short range order is frozen at T g which is further below the onset temperature T IC of the neutron intensity of the incommensurate AFM correlation.