Magnetic and electrical transport properties in the self-doped manganite La0.9Mn0.9M0.1O3 (M=Mn, Zn and Ti)

The magnetic and electrical transport properties of La0.9Mn0.9M0.1O3 (M=Mn, Zn and Ti) were investigated. The temperature and magnetic field dependence of electrical resistivity (ρ) and dc magnetization were studied. All the compounds are found in rhombohedral structure. The excess oxygen in all three compounds was detected through iodometric titration. A modification in resistivity is observed when M=Mn is replaced by M=Zn and Ti. The high temperature resistivity above TC follow variable range hopping model for both Zn and Ti compounds. For Zn doping, the observation of large field-cool effect and decrease in resistivity at room temperature and is assumed to be due to the implant of Mn4+ in Mn3+ matrix, which favor Mn3+/Mn4+ double exchange. The ferromagnetic behavior below TC for the compound with M=Ti is correlated to the excess oxygen in it, which implants Mn4+ and thus incorporates ferromagnetic interactions. The substitutions lead to a reduction of Tc and magnetization.