Rounding of a first-order magnetic phase transition in La0.7Ca0.3Mn0.85Ni0.15O3

We have prepared La0.7Ca0.3Mn0.91Ni0.09O3 and then studied its critical behavior and magnetocaloric effect. Analyzing temperature and field dependences of magnetization around the ferromagnetic-paramagnetic transition reveals the sample undergoing the second-order magnetic phase transition with the critical parameters TC ≈ 199.4 K, β = 0.171 ± 0.006, and γ = 0.976 ± 0.012. A considerable difference of these critical exponents compared with those expected for the standard models is due to the sample exhibiting the crossover property (tricriticality); its exponent values are more close to those expected for the tricritical mean-field theory with β = 0.25 and γ = 1. Under the field 40 kOe, the maximum magnetic entropy change (−ΔSmax) around TC is about 7.1 J·kg−1·K−1, corresponding to a refrigerant capacity RC ≈ 170 J/kg. Particularly, its magnetic-field dependence obeys a power law |ΔSmax| ∝ Hn, where n = 0.55 is quite far from the value calculated from the relation n = 1 + (β − 1)/(β + γ).

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Enhanced magnetocaloric performance in manganite bilayers

Yuan

Han

et al. 2020

Journal of Applied Physics

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Bilayer films of La0.8Sr0.2MnO3 and La0.7Ca0.3MnO3 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 ∼6.0J/kg, compared to a value of ∼4.2J/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.

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Rounding of a first-order magnetic phase transition in La0.7Ca0.3Mn0.85Ni0.15O3

Cited by 3 publications

References 15 publications

First-to-second-order magnetic-phase transformation in La 0.7 Ca 0.3-x Ba x MnO 3 exhibiting large magnetocaloric effect

First-to-second-order magnetic-phase transformation in La 0.7 Ca 0.3-x Ba x MnO 3 exhibiting large magnetocaloric effect

Crossover from first-order to second-order phase transitions and magnetocaloric effect in La0.7Ca0.3Mn0.91Ni0.09O3

Enhanced magnetocaloric performance in manganite bilayers

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