structual, magnetic, and transport properties of lamn_1-xcu_xo_3 (x= 0-0.125) ceramics

The present study investigates the structural, magnetic, and electrical properties of non-stoichiometric lamn1-xcuxo3 (x= 0, 0.025, 0.05, 0.075, and 0.125) ceramics. the results of x-ray diffraction refinement indicated that all samples were crystallized in an orthorhombic structure and no apparent crystal structure change was introduced by doping cu up to x=0.125. the ferromagnetic (fm) nature revealed by non-stoichiometric lamn1-xcuxo3- was verified through the appearance of paramagnetic-ferromagnetic (pm-fm) transition temperatures in ac magnetic susceptibility measurement of the samples. due to the coexistence of antiferromagnetic (afm) and fm phases, all samples contained re-entrant spin glass (rsg) and cluster spin glass (csg) states. the results showed that fm phase was comparable or even dominant in the doped samples up to x=0.075; however, after doping, afm phase overcame the fm phase as a result of reduction of double exchange interaction. temperature dependence of resistivity measurement indicated that upon increasing the cu-doping level, resistivity decreased, except for the x=0.125 sample, and that metal-insulator transition at low temperatures was detected in the doped samples. furthermore, changing the magnetic phase in the case of x=0.125 sample from fm (in x=0.075) to afm dominant phase was accompanied by changing the transport parameters obtained from small polaron hopping models.