  Two-sublattice ferrimagnet, with spin-$s_1$ operators $\bf{S_{1i}}$ at the
sublattice $A$ site and spin-$s_2$ operators $\bf{S_{2i}}$ at the sublattice
$B$ site, is considered. The magnon of the system, the transversal fluctuation
of the total magnetization, is a complicate mixture of the transversal
fluctuations of the sublattice $A$ and $B$ spins. As a result, the magnons'
fluctuations suppress in a different way the magnetic orders of the $A$ and $B$
sublattices and one obtains two phases. At low temperature $(0,T^*)$ the
magnetic orders of the $A$ and $B$ spins contribute to the magnetization of the
system, while at the high temperature $(T^*,T_N)$, the magnetic order of the
spins with a weaker intra-sublattice exchange is suppressed by magnon
fluctuations, and only the spins with stronger intra-sublattice exchange has
non-zero spontaneous magnetization. The $T^*$ transition is a transition
between two spin-ordered phases in contrast to the transition from spin-ordered
state to disordered state ($T_N$-transition). There is no additional symmetry
breaking, and the Goldstone boson has a ferromagnetic dispersion in both
phases. A modified spin-wave theory is developed to describe the two phases.
All known Neel's anomalous $M(T)$ curves are reproduced, in particular that
with "compensation point". The theoretical curves are compared with
experimental ones for sulpho-spinel $MnCr2S_{4-x}Se_{x}$ and rare earth iron
garnets.

Strongly Correlated Electrons