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

Abstract

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).

Magnetocaloric Effect, Dielectric Relaxor Behavior, and Evidence for Direct Magnetodielectric Behavior in Ni0.6Zn0.4Al0.5Fe1.5O4 Ceramics for High-Temperature Applications

“…At T = T C , however, n reached its minimum. The shape of n ( T ) behaves similar to that of the polycrystalline samples studied in the literature. − …”

Investigation of magnetic properties and colossal magnetoresistance in nanocrystalline doped manganite

“…According to mean field theory (MFT), if the system possesses second-order phase transition then plots of n vs. T are Near the T C , FM clusters and magnetic disorder are associated with this behaviour. In other perovskite systems, similar behaviour has been observed [59][60][61]. Additionally, all the n values are not stable but change with the temperature and field.…”

Role of lanthanum vacancy on the structural, magnetic and magnetocaloric properties in the lacunar perovskite manganites La0.8−x□xNa0.2MnO3(0 ≤ x ≤ 0.15)

“…A similar behavior has been observed in other perovskite materials. [47][48][49] According to the suggestion by Franco and Conde, 50 universal scaling analysis helps to determine the nature of the magnetic phase transition (rst or second order) in our samples. 51 This model can be conrmed by normalizing maximum magnetic entropy changes and temperatures, as dened by the following relation: 52…”