Double-exchange ferromagnetism and magnetoresistance in LaMn1−xCuxO3 (x⩽0.3)

We have studied the magnetic and magnetotransport properties of the perovskite LaMn1−xCuxO3 (x⩽0.3). All of these compounds show ferromagnetism and cluster glass behavior at low temperatures. Though no metallic-insulating transition associated with the ferromagnetic–paramagnetic transition appears, a large magnetoresistance was observed in the ferromagnetic phase. Due to the fact that the Cu ion in these compounds is divalent, the ferromagnetism in LaMn1−xCuxO3 is believed to be consistent with the Mn3+–O–Mn4+ double-exchange mechanism. These results suggest that double exchange and large magnetoresistance can be obtained by direct Mn-site doping.