title: Structural, magnetic and magnetocaloric effects in epitaxial La0.67Ba0.33Ti0.02Mn0.98O3ferromagnetic thin films grown on 001-oriented SrTiO3substrates.
abstract: Epitaxial La0.67Ba0.33Ti0.02Mn0.98O3(denoted as LBTMO hereafter) thin films of approximately 95 nm thickness were deposited by a pulsed laser deposition technique onto SrTiO3(STO) (001) substrates. High-resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM) investigations revealed that the films are epilayers with a four-fold symmetry around the [001] direction. Cross-sectional TEM and the presence of Pendellosung fringes in the XRD profiles demonstrate smooth interfaces. The STO substrate induces an in-plane compressive strain, which leads to a slight tetragonality of the film structure. The epilayers exhibit paramagnetic-to-ferromagnetic phase transitions at the Curie temperature TC(286 K), close to room temperature. The magnetization easy axis lies in the film plane along the [100] direction of the (001) substrate. The magnetic entropy change (ΔSM) associated with the second-order magnetic phase transition was determined via magnetization measurements in the temperature range between 210 and 350 K under different magnetic fields. The relative cooling power (RCP) of this film is about 220 J kg-1, somewhat lower than that of bulk Gd (410 J kg-1) for a 50 kOe field change, making the LBTMO ferromagnetic thin films a promising candidate for micro/nanomagnetic refrigeration around room temperature. The proposed universal curve provides a simple method for extrapolating ΔSMin a wide range of fields and temperatures, thus confirming the order of the magnetic transition in this system. The magnetic entropy (ΔSM)maxaround TCis proportional to (μ0H/TC)2/3in agreement with the mean-field theory, indicating the existence of long-range ferromagnetic interactions in epitaxial LBTMO thin films.
authors.affiliation: Laboratoire de Physico-Chimie des Matériaux, Université de Monastir, Monastir, Tunisia. oumezzine@hotmail.co.uk.
authors.forename: Marwène
authors.initials: M
authors.lastname: Oumezzine
authors.affiliation: Laboratory of Multifunctional Materials and Structures, National Institute of Materials Physics, Magurele, Romania. ac_galca@infim.ro.
authors.forename: Aurelian Catalin
authors.initials: AC
authors.lastname: Galca
authors.affiliation: Laboratory of Multifunctional Materials and Structures, National Institute of Materials Physics, Magurele, Romania. ac_galca@infim.ro.
authors.forename: Iuliana
authors.initials: I
authors.lastname: Pasuk
authors.affiliation: Laboratory of Multifunctional Materials and Structures, National Institute of Materials Physics, Magurele, Romania. ac_galca@infim.ro.
authors.forename: Cristina Florentina
authors.initials: CF
authors.lastname: Chirila
authors.affiliation: Laboratory of Magnetism and Superconductivity, National Institute of Materials Physics, Magurele, Romania.
authors.forename: Aurel
authors.initials: A
authors.lastname: Leca
authors.affiliation: Laboratory of Magnetism and Superconductivity, National Institute of Materials Physics, Magurele, Romania.
authors.forename: Victor
authors.initials: V
authors.lastname: Kuncser
authors.affiliation: Laboratory of Nanoscale Condensed Matter, National Institute of Materials Physics, Magurele, Romania and Faculty of Physics, University of Bucharest, Magurele, Romania.
authors.forename: Liviu Cristian
authors.initials: LC
authors.lastname: Tanase
authors.affiliation: Laboratory of Atomic Structures and Defects in Advanced Materials, National Institute of Materials Physics, Magurele, Romania and Faculty of Physics, University of Bucharest, Magurele, Romania.
authors.forename: Andrei
authors.initials: A
authors.lastname: Kuncser
authors.affiliation: Laboratory of Atomic Structures and Defects in Advanced Materials, National Institute of Materials Physics, Magurele, Romania.
authors.forename: Corneliu
authors.initials: C
authors.lastname: Ghica
authors.affiliation: Laboratoire de Physico-Chimie des Matériaux, Université de Monastir, Monastir, Tunisia. oumezzine@hotmail.co.uk.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Oumezzine