Critical Properties and Magnetocaloric Effect in La 0.7 Ba 0.3 Mn 0.8 Ti 0.2 O 3 Ceramic
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MANGANITE compounds with general formula R1xMxMnO3 (R = rare-earth ions, M = divalent alkaline-earth ions) have been intensively studied for potential applications in magnetic refrigeration, field sensors, and biomedicine. In particular, numerous studies have focused on extraordinary effects, such as colossal magnetoresistance (CMR) and magnetocaloric effect (MCE) occurring around the ferromagnetic (FM)–paramagnetic (PM) phase transition temperature (TC); as such, manganites remain a major research topic in the condensed matter field.[1–3] Some theoretical models have been proposed to explain the nature of magnetic phases and the origin of CMR and MCE in manganites. These effects were first interpreted based on the double-exchange (DE) interaction between Mn3+–Mn4+ pairs suggested by Zener[4] combined with L.V. BAU is with the Department of Engineering and Technology, Hong Duc University, 565 Quang Trung Street, Thanh Hoa City 440000, Viet Nam. O. MORA´N is with the Universidad Nacional de Colombia, Medellı´ n Campus, Facultad de Ciencias, Departamento de Fı´ sica, Advanced Oxides Group, A.A. 568, Medellı´ n 050000, Colombia. P.T. THO is with the Department of Physics and Technology, Thai Nguyen University of Science, Thai Nguyen City 250000, Viet Nam. P.T. PHONG is with the Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 700000, Viet Nam and also with the Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 700000, Viet Nam. Contact e-mail: [email protected] Manuscript submitted September 6, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
the Jahn–Teller distortion of MnO6 octahedra in perovskite structures.[5] The definition of the Griffiths phase[6] and the phase separation mechanism[7] were introduced to clarify these phenomena. Considering the potential applications and the rich physical properties of manganites, studies on magnetic exchange are of key importance for deepening the understanding of magnetic ordering and for providing a basis for the upcoming application of magnetic refrigeration devices and other devices in spintronics. Insights into thermodynamic processes will help optimize the design of a new magnetic refrigeration. Studying the theory of critical phenomena, which predict the existence of a universal behavior in materials with second-order magnetic phase transition, is necessary to clarify this issue.[8] Thus, the study of critical exponents associated with phase transitions is of pivotal importance. The long-range meanfield theory was first utilized to determine the critical behavior in the double-exchange model.[9] However, recent theoretical works have shown that the critical behavior of doped manganites can be characterized based on short-range interactions as specified by the Heisenberg model.[10,11] Nevertheless, experimental results pertaining to the critical exponents of manganites remain controversial within the framework of the Heisenberg,[12–14] mean field,[15,16] 3D Ising,[1
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