The effects of Jahn–Teller distortion changes on transport propertiesin LaMn1−xZnxO3

Abstract

The magnetism and magnetotransport properties of dopedperovskite LaMn1−xZnxO3(x = 0.05,0.10, 0.15, 0.20, 0.30, 0.40) have been studied. All samples exhibitinsulating behaviour under zero field and a 6 T field (except forx = 0.05,the weak insulating–metallic transition occurs nearTC under zerofield), but there is a paramagnetic–ferromagnetic (PM–FM) transition and a large MR effectnear TC. Theρ– Tcurves are fitted well by a semiconductor-like model. We suggest that the MnO6octahedron is contorted by zinc doping and that this contortionwill influence the Jahn–Teller (JT) distortion of Mn3+. Theegcarrier has to overcome the energy gap caused by thedifference between the JT distortions induced by Mn3+ in the non-contortedMnO6octahedrons and the contorted ones. Infrared spectra and Raman spectraconfirmed our ideas. In addition, the magnetism was investigated by ESR andM–Tmeasurements. The Zn doping suppresses the PM–FM transition andTC decreases with theincrease of dopant. For x = 0.30and 0.40, there exists cluster–glass behaviour in the low-temperature range.