Abstract: Polycrystalline samples of La_0.4Ca_o.6Mn_{1 - x} Cr _xO₃ ( x =0.00,0.02,0.04,0.06,0.08,0.10,0.15 ) were prepared by t he solid state reaction method. The influence of Cr³⁺ substitution for Mn³⁺ on the magnetic property and charge ordering phase of La_0.4Ca_0.6MnO₃ was studied through the measurements of X-ray diffraction (XRD), magnetization- temperature ( M-T) curves and electron spin resonance (ESR) spectra. The experimental results indicate that the sample of La_0.4Ca_0.6MnO₃ has very complicated magnetic structure. The charge ordering phase of the sample exhibits at 258K, and strong correlated CO-AFM phase shows from 175K to 50K. The spin glass state of the sample appears when the temperature decreases to about 41K. When the Cr substitution amount x is more than 0.06, the charge ordering phase of the sample is destroyed. When x is larger than 0.10, spin-glass state is melt. In addition, experimental resu lts are explained preliminarily as follows: because Cr³⁺ and Mn⁴⁺ have the same electronic structure, Cr³⁺ substitution for Mn³⁺ destroys the spin order of CE-type antiferromagnetism, and thus leads to the destruction of charge ordering. It is verified experimentally that the strong coupling between charge ordering and spin ordering exists in the charge order system of CE-type anti-ferromagnetism, and Cr³⁺ substitution for Mn³⁺ destroys formation conditions of spin-glass state that small ferromagnetic component exists at the background of antiferromagnetism.

Key words: La_0.4Ca_o.6MnO₃, Cr-doping, charge ordering, spin-glass state