MAGNETIC AND TRANSPORT-PROPERTIES OF EUMNO3+X SUBSTITUTED BY CA, SR AND CR IONS

The magnetic properties of EuMnO3+x1 Eu(Mn1-xCrx)O-3, Eu1-xCaxMnO3 and Eu1-xSrxMnO3 were investigated. It is established that EuMnO3 is a we ak ferromagnet with Neel temperature T-N = 49 K. The increasing oxygen content leads to decreasing T-N. The substitution of Eu by Ca and Sr causes a strong increase in magnetization and temperature of magnetic ordering, however, a truly ferromagnetic state does not occur in these systems. The insulating Eu0.7Sr0.3MnO3 exhibits a ''colossal'' magnet oresistance effect which increases strongly with decreasing temperatur e. It is assumed that Eu(Mn1-xCrx)O-3 (0.2 less than or equal to x les s than or equal to 0.5) solid solutions are mictomagnets with poorly d efined temperatures of magnetic ordering. The results are explained in terms of superexchange via anions.