Magnetic state is a partial ordered state if only part of the electrons in the system give contribution to the magnetic order. We study Heisenberg model of two sublattice spin system, on the body-centered cubic lattice, with antiferromagnetic nearest neighbors exchange of sublattice A and B spins and two different ferromagnetic exchange constants for sublattice A (JA) and B (JB) spins. When JA>JB the system undergoes transition from paramagnetism to ferromagnetism at Curie temperature TC. Only the sublattice A spins give contribution to the magnetization of the system. Upon cooling, the system possesses ferromagnetism to antiferromagnetism transition at Néel temperature TN<TC. Below TN sublattice A and B electrons give contribution to the magnetization. The transition is a partial ordered transition. There is thermodynamic evidence for this transition in the magnetic specific heat of the system. As a function of temperature there are two maxima. At high temperature TC it is λ-type. At lower temperature TN it characterizes the transition from ferromagnetism to antiferromagnetism. As an example of ferromagnetism to antiferromagnetism partial ordered transition we consider the material La1−xCaxMnO3 in the doping range x≥0.50. Our calculations reproduce the experimental magnetization-temperature curve.