μμSR study of AA3′Mn4O12 double perovskites

Zero-field μμSR experiments were performed on a series of polycrystalline samples of AA3′Mn4O12 double perovskites (A=Na+,Ca2+(A=Na+,Ca2+, La3+La3+; A′=Cu2+A′=Cu2+, Mn3+Mn3+) synthesized under high pressure. Spontaneous precession frequencies, of comparable magnitude to those previously reported in LaMnO3LaMnO3, were observed in all the family members except CaMn7O12CaMn7O12. For all the samples, μμSR yielded determinations of the magnetic transition temperatures and of the order parameter in agreement with other techniques, but also revealed a peculiar phase separation in CaMn7O12CaMn7O12, absent in the other compounds.