Influence of Ca-deficiency on the magneto-transport properties in La0.8Ca0.2MnO3 perovskite and estimation of magnetic entropy change

Abstract

La 0.8 Ca 0.2 À x h x MnO 3 (x ¼ 0.00, 0.10, and 0.20) perovskite was prepared by the conventional solid-state reaction and annealed at 1473 K. X-ray diffraction and scanning electron microscopy shown the existence of a secondary phase attributed to the unreacted Mn 3 O 4 oxide. The magneto transport properties have been investigated based on the temperature dependence of the resistivity q(T) measurements under several applied magnetic fields. We note that the La 0.8 Ca 0.2 MnO 3 (x ¼ 0.00) sample has a classical metal-insulator transition at T q . But we have observed that the lacunars samples (x ¼ 0.10 and 0.20) include a metallic and insulator behavior simultaneously below T q and the resistivity is dominated by tunneling through the barriers associated with the insulating phase. In other words, the calcium deficiency favors the enhancement of the insulator behavior. The electrical resistivity is fitted with the phenomenological percolation model, which is based on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. Furthermore, we found that the estimated results are in good agreement with experimental data. Above all, the resistivity dependence on the temperature and magnetic field data is used to deduce the magnetic entropy change. We have found that these magnetic entropy change values are similar to those calculated in our previous work from the magnetic measurements. Finally, we have found an excellent estimation of the magnetic entropy change based on the Landau theory.

Investigation on structural, magneto-transport, magnetic and thermal properties of La0.8Ca0.2−xBaxMnO3 (0⩽x⩽0.2) manganites

“…It is observed that as Ba-content increases, the metal insulator transition temperature T MI monotonically shifts towards higher temperature region. Pristine sample exhibits T MI around 210 K, which is matching with that reported in literature [13,28]. We now explain the reasons for the observed increase of T MI with Ba content.…”

“…In particular La 1-x Ca x MnO 3 (LCMO) compounds have attracted extra attention because of occurrence of enormous magneto-resistance (MR) and huge magneto-caloric effect (MCE) which makes them good candidates for applications [5][6][7][8][9][10][11][12][13][14][15].…”

Investigation on magnetic, electrical and thermoelectric power of Bi-substituted La0.8Ca0.2MnO3 manganites

“…GP in the case of La 1-x Ca x MnO 3 is believed to arise from the disorders arising from the tilting of MnO 6 octahedron [8,13] where as the static Jahn-Teller distortion leads to GP in La 1-x Sr x MnO 3 system [12]. Nevertheless, there are contradictory reports [14,15,16] on the existence of GP in La 0.8 Ca 0.2 MnO 3 system. Khlifi et al [14] and Zang et al [15] have observed the absence of GP in La 0.8 Ca 0.2 MnO 3 system whereas Fatnassi et al [16] have reported the presence of GP.…”

“…Khlifi et al [14] and Zang et al [15] have observed the absence of GP in La 0.8 Ca 0.2 MnO 3 system whereas Fatnassi et al [16] have reported the presence of GP. It may be mentioned that Khlifi et al [14] have reported introduction of GP when calcium deficiency is brought into La 0.8 Ca 0.2 MnO 3 system.…”

Correlation between magnetic and electric properties based on the critical behavior of resistivity and percolation model of La0.8Ba0.1Ca0.1MnO3 polycrystalline

“…This makes them good candidates for a wide variety of applications. [4][5][6][7][8] As regards the La 1Àx Ca x MnO 3 compounds, they have a disadvantage that their Curie temperatures, T C , are well below room temperature. On the other side, doping Ca sites with large ions, for example Pb, Ba and Sr, has been explored by several researchers.…”