title: Magnetocaloric effect and critical behavior in Pr0.5Sr0.5MnO3: an analysis of the validity of the Maxwell relation and the nature of the phase transitions.
abstract: The Maxwell relation, the Clausius-Clapeyron equation, and a non-iterative method to obtain the critical exponents have been used to characterize the magnetocaloric effect (MCE) and the nature of the phase transitions in Pr0.5Sr0.5MnO3, which undergoes a second-order paramagnetic to ferromagnetic (PM-FM) transition at TC ~ 247 K, and a first-order ferromagnetic to antiferromagnetic (FM-AFM) transition at TN ~ 165 K. We find that around the second-order PM-FM transition, the MCE (as represented by the magnetic entropy change, ΔSM) can be precisely determined from magnetization measurements using the Maxwell relation. However, around the first-order FM-AFM transition, values of ΔSM calculated with the Maxwell relation deviate significantly from those calculated by the Clausius-Clapeyron equation at the magnetic field and temperature ranges where a conversion between the AFM and FM phases occurs. A detailed analysis of the critical exponents of the second-order PM-FM transition allows us to correlate the short-range type magnetic interactions with the MCE. Using the Arrott-Noakes equation of state with the appropriate values of the critical exponents, the ﬁeld- and temperature-dependent magnetization [Formula: see text] curves, and hence the [Formula: see text] curves, have been simulated and compared with experimental data. A good agreement between the experimental and simulated data has been found in the vicinity of the Curie temperature TC, but a noticeable discrepancy is present for [Formula: see text]. This discrepancy arises mainly from the coexistence of AFM and FM phases and the presence of ferromagnetic clusters in the AFM matrix.
authors.affiliation: Department of Physics, University of South Florida, Tampa, FL 33620, USA. Departamento de Física de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, 41080 Sevilla, Spain. Departamento de Física, Universidad de Oviedo, 33007 Oviedo, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Caballero-Flores
authors.forename: N S
authors.initials: NS
authors.lastname: Bingham
authors.forename: M H
authors.initials: MH
authors.lastname: Phan
authors.forename: M A
authors.initials: MA
authors.lastname: Torija
authors.forename: C
authors.initials: C
authors.lastname: Leighton
authors.forename: V
authors.initials: V
authors.lastname: Franco
authors.forename: A
authors.initials: A
authors.lastname: Conde
authors.forename: T L
authors.initials: TL
authors.lastname: Phan
authors.forename: S C
authors.initials: SC
authors.lastname: Yu
authors.forename: H
authors.initials: H
authors.lastname: Srikanth
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004735:Energy Transfer; D060526:Magnetic Fields; D017895:Manganese Compounds / Q000737:chemistry*; D008956:Models, Chemical; D010087:Oxides / Q000737:chemistry*; D044367:Phase Transition; D011221:Praseodymium / Q000737:chemistry*; D013324:Strontium / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide; D011221:Praseodymium; D013324:Strontium