Critical Parameters and Magnetocaloric Effect of the La&amp;lt;sub&amp;gt;5/8&amp;lt;/sub&amp;gt;Ca&amp;lt;sub&amp;gt;3/8&amp;lt;/sub&amp;gt;Mn&amp;lt;sub&amp;gt;0.9750&amp;lt;/sub&amp;gt;Pd&amp;lt;sub&amp;gt;0.025&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; Compound

L V Bau,N M An

doi:10.4236/msa.2014.512086

Abstract

The La5/8Ca3/8Mn0.9750Pd0.025O3 compound was studied using DC magnetization measurements. The data were analyzed in the paramagnetic-ferromagnetic phase transition region by the Arrott plot method. The results show the Curie temperature TC ~ 247.8 K and the critical exponents of b = 0.48633, g = 1.18623 and d = 3.431682. The values of the critical exponents are between the mean- field theory and 3D Ising model. The magnetocaloric value is ~5 J/kgK, extracted from the M(H) curves.

Highlights

The Curie temperature TC, colossal magnetoresistance (CMR) perovskite manganites behave paramagnetic insulating state
It is shown that the ferromagnetic clusters are formed and extracted as decreasing temperature below TC
The existence of ferromagnetic clusters above TC [1] as well as inhomogeneity and phase separation [2] suggests that ferro-magnetic long-range order may be established by percolation of ferromagnetic regions as the temperature is lowered

Summary

Introduction

The Curie temperature TC, colossal magnetoresistance (CMR) perovskite manganites behave paramagnetic insulating state. The existence of ferromagnetic clusters above TC [1] as well as inhomogeneity and phase separation [2] suggests that ferro-magnetic long-range order may be established by percolation of ferromagnetic regions as the temperature is lowered Such magnetic inhomogeneities in the spin systems may be a result in a reduced local effective topological dimensionality [3], thereby leading to different critical behaviors. Static dc-magnetization measurements [4]-[7], in addition to β, yield the critical parameters γ and δ for initial susceptibility χ(T) and critical isotherm M(T, H), respectively They may fail to determine a unique universality class for the phase transition of these manganites. We report the critical parameters β, γ and δ determined from the Arrott plots, Arrott plots modified and magnetocaloric effects of the La5/8Ca3/8Mn0.975Pd0.025O3 compound by analyzing the magnetization curves

Experiments

Results and Discussion

Conclusion