Magnetic correlations in mixed valent layered La1.2Sr0.8CoO4

We present here investigations on a hole doped layered perovskite, La_1.2Sr_0.8CoO₄. In these systems concentration of the holes in host matrix decides ratio of the Co²⁺/Co³⁺ and magnetic phase diagram. In addition, spin-state of the Co³⁺ ions has an important role in magnetic correlations. Magnetization measurements show the signature of some exotic phases like cluster glass or canonical spin-glass and ferromagnetic ordering (T_c ∼ 211 K). In addition, calculated temperature variation of order parameter by also including the spin-state variations of Co³⁺ manifests that the orbital magnetic moments are not quenched here and has an important role in overall magnetic moment at low temperatures.