Effects of Cu Substitution on Magnetic Properties of Ca $_{3}$ Co $_{2}$ O

We report the magnetic properties of quasi-one-dimensional complex oxides Ca₃Co_2-xCu_xO₆ (x = 0, 0.02, 0.04, and 0.1). The rhombohedral structure (space group R[3̅]c ) peaks were well indexed in X-ray diffraction pattern. Ca₃Co₂O₆ shows a magnetic transition at around 27 K, whereas the transition temperature for Ca₃Co_1.9Cu_0.1O₆ is around 24 K. The magnetization steps tend to disappear, revealing that they are sensitive to the Cu substitution similar to the manganese or chromium substitution systems. These results indicate that the Cu²⁺ ions with spin state (S = 1/2) are antiferromagnetically coupled to their Co³⁺ neighbors so that the ferromagnetic coupling interaction is reduced.