Strain induced extrinsic magnetocaloric effects in La_0.67Sr_0.33MnO₃ thin films, controlled by magnetic field

The magnetic control of strain-induced giant caloric properties of epitaxial La_0.67Sr_0.33MnO₃ (LSMO) thin films grown on (0 0 1) BaTiO₃ (BTO) single crystal substrates is investigated. Arising from the crystallographic structural transformation of the BTO substrate during its 3-phase transitions, there is a drastic change of 3D film-lattice strain, which affects the local magnetic anisotropy of the LSMO at the interface and changes the entropy of the film. The thermal hysteresis observed in temperature dependent resistivity measurement can be manipulated by applying a magnetic field. Detailed transport and magnetic studies in different crystal orientations reveal the origin of such field-dependent magnetocaloric properties induced by the different phase transitions of the BTO substrate. Finally, a large entropy change of 1.03–1.95 J · Kg⁻¹ · K⁻¹ · T⁻¹ was obtained at the monoclinic–tetragonal (M–T) transition at 283 K which compares to  <1 J · Kg⁻¹ · K⁻¹ · T⁻¹ for previously reported films. (paper)