  The magnetic nature of the B-site dopants controls the magnetic phases in
B-site doped manganites RE$_{1-x}$AE$_{x}$Mn$_{1-\eta}$B$_{\eta}$O$_3$.
Different B-site dopants of equal valence, doped into the same reference
manganite, lead to different magnetic phases at low temperature, which can not
be explained using the valence change scenario. We focus on trivalent B-site
dopants in CE-CO-OO-I manganites at half-filling $x=0.50$ to study the role of
magnetic interactions between the B-site dopants and the neighboring Mn-sites
by using a two-orbital double-exchange model including super-exchange
interactions, Jahn-Teller lattice distortions and substitutional disorder in
two dimensions. We show that the magnetic reconstructions around the B-site
dopants due to the modified double-exchange and super-exchange interactions
control the phase competition in B-site doped manganites.
