Magnetic and electrical behaviour of La₀.₆₇Ba₀.₃₃Mn₁-ₓFexₒ₃ perovskites
Date
2010Author
Baazaoui, M.
Zemni, S.
Boudard, M.
Rahmouni, H.
Gasmi, A.
Selmi, A.
Oumezzine, M.
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We have investigated the effect of Fe 3+ substitution on electrical and magnetic properties of La₀.₆₇Ba₀.₃₃Mn₁-ₓFexₒ₃ (0 ≤ x ≤ 0.2) manganese perovskites. Polycrystalline samples were prepared by the conventional ceramic method at 1180ºC. Grain size and phase identification of specimens were carried out by X-ray diffraction techniques and morphological analysis by scanning electron microscope (SEM). The structure refinement by the Rietveld method revealed that all the compounds are a single phase manganite crystallizing in a rhombohedral (R3C) perovskite structure. Magnetization as a function of temperature, M (T) in zero field cooled (ZFC) mode, shows a paramagnetic (PM) to ferromagnetic (FM) phase transition below 10% iron concentration and a spin glass-behaviour above. Magnetization as a function of magnetic field measurement at 10K shows that below 10% Fe3+ doping, the materials exhibit a strong ferromagnetic behaviour, while above that concentration; aantiferromagnetic behaviour is predominant for specimens. Electrical-resistivity measurement in the temperature range 80 - 320K shows metal - semiconductor transition at peak temperature Tp below 10% Fe3+ ion doping with a decrease in Tp and increase in the maximum of resistivity (ρmax). Above 10% Fe3+ amount the materials exhibit only a semiconductor-like behaviour. Interestingly, with the increase in doping concentration, Tc and Tp follow the same trend indicating coupling of electric and magnetic properties. Changes in these properties have been analysed on the basis that the substitution of Fe3+ for Mn3+ reduces the number of available hopping sites for the Mn eg (↑) electron and suppresses the double exchange (DE), rather than lattice effect which is insignificant due to similar ionic radii of Fe3+ and Mn 3+.