The properties of the MoSr2RCu2O8 (R=rare earth) system are found to systematically change with the contraction of the R ions. For the light R ions (La-Nd) the samples are paramagnetic down to 5 K, whereas in the intermediate range (Sm-Tb), the Mo sublattice orders antiferromagnetically at TN, ranging from 11 to 24 K. For the heavy R ions, Ho-Tm and Y, superconductivity appears at TC in the range 19-27 K and antiferromagnetism sets in at TN < TC. This latter behavior resembles most of the magneto-superconductors, but is in sharp contrast to the iso-structural RuSr2RCu2O8 system where TN > TC.
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