Abstract
In this work, we present the results of the magnetic, critical, and magnetocaloric properties of the rhombohedral-structured La0.55Bi0.05Sr0.4CoO3 cobaltite. Based on the modified Arrott plot, Kouvel–Fisher, and critical isotherm analyses, we obtained the values of critical exponents (β, γ, and δ) as well as Curie temperature (TC) for the investigated compound. These components were consistent with their corresponding values and they were validated by the Widom scaling law and scaling theory. The obtained critical exponents were close to the theoretical prediction of the mean-field model values, revealing the characteristic of long-range ferromagnetic interactions. The magnetic entropy, heat capacity, and local exponent n(T, μ0H) of the La0.55Bi0.05Sr0.4CoO3 compound collapsed to a single universal curve, confirming its universal behaviour. The estimated spontaneous magnetization value extracted through the analysis of the magnetic entropy change was consistent with that deduced through the classical extrapolation of the Arrott curves. Thus, the magnetic entropy change is a valid and useful approach to estimate the spontaneous magnetization of La0.55Bi0.05Sr0.4CoO3.
Highlights
As a member of perovskite oxides, cobaltites are important agile and multifunctional materials that are very promising for several applications, including high-temperature oxygen separation membranes, cathodes in solid oxide fuel cells (SOFCs), magnetic storage, and magnetic refrigeration.[1,2,3] The Co-based sister compounds of manganites have been less intensively studied.[4,5,6] It is well-known that the similar Hund's rule exchange energy and crystal- eld energy both lead to an additional spin-state degree of freedom in cobaltites, which results in close competition between the multiple ground states
We conducted an in-depth investigation on magnetic, critical behavior, and MCE effect on La0.55Bi0.05Sr0.4CoO3 cobaltite synthesized via the solid-state reaction
The magnetic properties reveal that our sample undergoes a FM–PM second-order magnetic transition, which can be con rmed from the Arrott curves and universal curves of magnetic entropy changes
Summary
Physical effects such as magnetoresistance and magnetocaloric effects observed in manganites[10,11] and cobaltites[3,12,13,14] have been the subject of several investigations in the last few years. Double exchange (DE), phase separation (PS), Jahn–Teller distortion (JT), and Griffiths phase (GP) have been found to explain the aforementioned effects These compounds are interesting for applications since they present low costs and longer usage times. The theory of critical phenomena justi ed the existence of a universal MCE behavior in materials exhibiting second-order magnetic phase transitions.[17] Recent studies have revealed the impact of Bi3+ substitution on several properties in La-based manganites.[18,19,20] It is believed that the BiMnO3 system is a special and promising compound, which exhibits multiferroic properties where phases like ferroelectric, FM, and ferroelastic coexist in this oxide. The present investigation is an attempt to ll this gap to a certain extent and to comprehensively explore the magnetic transition nature of a La0.55Bi0.05Sr0.4CoO3 system
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