Universal critical behavior in polycrystalline La0.75Ca0.25-xNaxMnO3 (x = 0.00; 0.05) samples
Laboratoire de la Matière Condensée et des Nanosciences, LR11ES40, Département de Physique, Faculté des Sciences de Monastir, Université de Monastir, 5019, Monastir, Tunisia
2 Laboratoire des Energies et des Matériaux, LabEM-LR11ES34, Ecole Supérieure des Sciences et de la Technologie, University of Sousse, Road Lamine Abessi, Hammam Sousse, 4011, Sousse, Tunisia
3 Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000, Grenoble, France
Accepted: 19 November 2020
Published online: 3 January 2021
The critical behavior of the manganese La0.75Ca0.25−xNaxMnO3 (x = 0.00; 0.05) was studied around the PM-FM phase transition. Various techniques are used to obtain the critical exponents of our samples; such as modified Arrott plot (MAP), Kouvel–Fisher (KF) method and the critical isotherm analysis (CI) around the Curie temperature (Tc). The experimental results indicated that our samples had a second-order magnetic phase transition. Based on the above methods, the critical exponents (β, γ and δ) were extracted in the low- and the high-magnetic fields from the magnetic isotherms data. The obtained critical exponents were close to those expected for the Tricritical Mean-Field model. These critical exponents obey to the Widom scaling relation δ = 1 + γ/β, which proves the reliability and the self-consistency of all critical exponents values. The magnetization–field–temperature (M–µ0H–T) falls into two curves, below and above TC. It follows the single scaling equation with ε = (T–TC)/TC is the reduced temperature. This confirms the reasonability of the critical exponents with the scaling hypothesis. Moreover, the analysis of the effective exponents βeff and γeff indicates that βeff (ɛ) for the two samples and γeff (ɛ) for x = 0.00 are self-consistency and in good agreements with the Tricritical mean-Field model, but γeff (ɛ) for x = 0.05 is heterogeneous with any class of predicted universality.
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