Rare earth effect on structural, magnetic and magnetocaloric properties of La0.75Ln0.05Sr0.2MnO3 manganites

Effect of charge ordering and phase separation on the electrical and magnetoresistive properties of polycrystalline La 0.4 Eu 0.1 Ca 0.5 MnO 3

In this paper, we have investigated the electrical and magnetic response of a La0.4Gd0.1Ca0.5MnO3 polycrystalline sample. This sample seems to exhibit fascinating phenomena like charge ordering, magnetic phase separation, training effects and kinetic arrest. It also shows colossal values of negative magnetoresistance (∼91.7% at 96 K under 1 T applied magnetic field), which raises the possibility of using this sample for technological applications. We have also proposed, in this work, a new empirical model to describe the evolution of resistivity and magnetoresistance as a function of magnetic field. This model was successfully tested on the La0.4Gd0.1Ca0.5MnO3 sample in spite of its complicated magnetic behavior, which suggests the use of this model for other magnetic samples in order to check its validity.

An empirical model for magnetic field dependent resistivity and magnetoresistance in manganites: application on polycrystalline charge-ordered La0.4Gd0.1Ca0.5MnO3

In this paper, we have studied the effect on the structural, magnetic and magnetocaloric properties of La and Sr-deficiencies in the La0.67Sr0.33MnO3 compound. Rietveld refinement of the X-ray powder diffraction patterns confirms that all of the compounds have crystallized into a rhombohedral crystal symmetry with an R3[combining macron]c space group. X-ray photoelectron spectroscopy measurements revealed that the parent compound has a mixed valance of Mn3+/Mn4+, whereas Mn2+/Mn3+/Mn4+ mixed valency is found in the case of both La and Sr-deficient compounds. The La0.67Sr0.33MnO3 compound shows a magnetic transition temperature of 365 K, while the La and Sr-deficient compounds exhibit transition temperatures of 367 K and 355 K, respectively. Among the studied compounds, the Sr-deficient compound shows the highest magnetic entropy change (ΔSM) of 5.08 J kg-1 K-1 at 352 K for a 50 kOe field with a relative cooling power (RCP) of 142 J kg-1 and an adiabatic temperature change of 3.48 K, while the parent and La-deficient compounds exhibit a -ΔSM of 4.78 J kg-1 K-1 at 364 K and of 4.12 J kg-1 K-1 at 364 K, respectively. The temperature dependence of the electrical resistivity with and without applied magnetic fields reveals that the La-deficient compound has one order and the Sr-deficient compound has two orders of suppression in the electrical resistivity. Thus, the Sr-deficient compound shows promising behaviour for reduction of the magnetic transition temperature towards room temperature, along with an increase in the ΔSM values, and enhancement in the electrical conductivity. Therefore, it could be possible to tune the transition temperature towards room temperature without compromising the magnetic entropy change in order to develop materials for magnetic refrigeration applications.

S. Mukherjee

Papers

Transport and magnetoresistance studies on polycrystalline La 0.4 Dy 0.1 Ca 0.5 MnO 3 : Role of phase separation

Effect of charge ordering and phase separation on the electrical and magnetoresistive properties of polycrystalline La 0.4 Eu 0.1 Ca 0.5 MnO 3

An empirical model for magnetic field dependent resistivity and magnetoresistance in manganites: application on polycrystalline charge-ordered La0.4Gd0.1Ca0.5MnO3

Magnetic phase separation in polycrystalline Pr0.5−xBixSr0.5MnO3 (x ≤ 0.15)

Charge transport mechanisms and magnetoresistance behavior of La0.6Pr0.1Ca0.3MnO3 manganite