Muon-spin-relaxation study of magnetic order in RNiO3 ( R =rare earth) below the metal-insulator transition

International audienceResistivity and susceptibility measurements on the perovskite Nd0.7La0.3NiO3 reveal the coincidence of magnetic and metal-insulator transitions at TMI=110 K. Muon-spin-relaxation (μSR) has been used to characterize the magnetic order in the low-temperature insulating phase. Two magnetically inequivalent muon sites exist there below TMI. It is found that the crystallographically equivalent rare-earth planes split into two magnetically inequivalent planes below TMI, one plane containing ordered Nd ions, the other remaining paramagnetic down to low temperatures. This behavior is a consequence of the unusual magnetic order of the Ni ions below TMI, with the μSR data confirming the disappearance of the inversion center at the Ni site in the magnetic insulating regime of the RNiO3 perovskites