The magnetic phase diagram of highly anisotropic double-exchange model syst
ems is investigated as a function of the ratio of the anisotropic hopping i
ntegrals, i.e., t(c)/t(ab), on a three-dimensional lattice by using Monte C
arlo calculations. The magnetic domain structure at low temperature is foun
d to be a generic property of the strong anisotropy region. Moreover, the t
(c)/t(ab) ratio is crucial in determining the anisotropic charge transport
due to the relative spin orientation of the magnetic domains. As a result,
we show the anisotropic hopping integral is the most likely cause of the ma
gnetic domain structure. It is noted that the competition between the reduc
ed interlayer double-exchange coupling and the thermal frustration of the o
rdered two-dimensional ferromagnetic layer seems to be crucial in understan
ding the properties of layered manganites.