Enhanced magnetocaloric performance in manganite bilayers

Bilayer films of La 0.8 Sr 0.2 MnO 3 and La 0.7 Ca 0.3 MnO 3 with different layer thicknesses and stacking sequences were synthesized via pulsed laser deposition. The magnetic properties and magnetocaloric effects were systematically investigated. We found that the phase transition associated with the layers tends to merge together at an optimal thickness and a stacking sequence. The operating temperature span of the entropy change broadens at the expense of its magnitude, leading to an enhancement of the refrigerant capacity by over 40%. The optimized bilayer film possesses a refrigerant capacity of ∼ 6.0 J / kg, compared to a value of ∼ 4.2 J / kg for the single-phase films. The phase transition broadening induced by epitaxial strain is responsible for the enhanced window of operating temperature as well as refrigerant capacity. The design principle developed here may be applied to ferroelastic and ferroelectric materials to enhance elastocaloric and electrocaloric effects.