Critical Behavior of La0.8Ca0.2Mn1−xCoxO3 Perovskite (0.1 ≤ x ≤ 0.3)

Dorra Turki,Mohamed Ellouze,Khaled Elsaid,Ahmed Easa,M Ahmad,Foued Elhalouani,Saeed Al-Meer,El Hlil,Gyorgy Remenyi,Sami Mahmood,Zafar Ghouri

doi:10.3390/magnetochemistry3030028

Abstract

The critical properties of La0.8Ca0.2Mn1−xCoxO3 (x = 0, 0.1, 0.2 and 0.3) compounds were investigated by analysis of the magnetic measurements in the vicinity of their critical temperature. Arrott plots revealed that the paramagnetic PM-ferromagnetic (FM) phase transition for the sample with x = 0 is a first order transition, while it is a second order transition for all doped compounds. The critical exponents β, γ and δ were evaluated using modified Arrott plots (MAP) and the Kouvel-Fisher method (KF). The reliability of the evaluated critical exponents was confirmed by the Widom scaling relation and the universal scaling hypothesis. The values of the critical exponents for the doped compounds were consistent with the 3D-Heisenberg model for magnetic interactions. For x = 0.1, the estimated critical components are found inconsistent with any known universality class. In addition, the local exponent n was determined from the magnetic entropy change and found to be sensitive to the magnetic field in the entire studied temperature range.

Highlights

Several investigations had been carried out on the sensitivity of the physical properties of manganites to the substitution of Mn cations at B-sites by trivalent and tetravalent ions such as Fe, Co, Mo and Cr [1,2,3,4]
Since the values of critical exponents play an important role in elucidating the interaction mechanisms near the Curie temperature (TC) and identifying the universality class of the material, several studies focused on investigating the critical behavior of manganites in the vicinity of TC [12,13]
The discontinuous ferromagnetic-paramagnetic FM-PM transition at TC as a consequence of structural changes is a first-order magnetic transition (FOMT) [14,15,16]. This discontinuous phase transition can evolve into a continuous second-order magnetic phase transition (SOMT) upon doping the manganite [17]

Summary

Introduction

Several investigations had been carried out on the sensitivity of the physical properties of manganites to the substitution of Mn cations at B-sites by trivalent and tetravalent ions such as Fe, Co, Mo and Cr [1,2,3,4]. Previous studies on La0.8Ca0.2MnO3-based materials indicated FOMT and/or second-order magnetic transition (SOMT) [22,23].

Results

Conclusion