Magnetic properties of cubic La_1-xCa_xMnO₃ (0 ≤ x ≤ 0.4) are investigated between T = 5 and 310 K in the external field of 2 G. The dependence of the ferromagnetic transition temperature on x is analyzed with the model of spin polarons associated with electronic localization and electron-electron interaction. The bandwidth of the localized electrons is found to be W = 1.90 ± 0.05 eV. In the samples with x < 0.2 and the Mn⁴⁺ concentration c < 0.26, a transition to a canted antiferromagnetic spin state is observed. The dependence of the transition temperature, T₁, on c can be well described by a model including the Mn³⁺-Mn³⁺ superexchange and the Mn³⁺-Mn⁴⁺ double-exchange interactions. In the samples with x ≤ 0.2 and c ≤ 0.22 the value of the critical exponent, γ = 1.21 ± 0.05, is obtained for the temperature dependence of the zero-field-cooled susceptibility function χ^-1 (T) approx. (T - T_C)^γ, for T > T_C.