The magnetocaloric effect with critical behavior of a periodic Anderson-like organic polymer. Issue 1 (30th November 2015)

• Record Type: Journal Article
• Authors: Ding, L. J.; Zhong, Y.; Fan, S. W.; Zhu, L. Y.
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 1(2016)
• Page Start: 510
• Page End: 518
• Publication Date: 2015-11-30
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c5cp06137g
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The magnetic entropy change (−Δ S ) shows a double-peak structure, indicating a double magnetic cooling process via demagnetization. Abstract : We study the magnetocaloric effect and the critical behavior of a periodic Anderson-like organic polymer using Green's function theory, in which the localized f orbitals hybridize with the conduction orbitals at even sites. The field-induced metal–insulator transitions with the magnetic Grüneisen parameter showing | Γ h | ∼ T −1 power-law critical behaviour are revealed, which provides a new thermodynamic means for probing quantum phase transitions. It is found that the competition of up-spin and down-spin hole excitations is responsible for the double peak structure of magnetic entropy change (−Δ S ) for the dominant Kondo coupling case, implying a double magnetic cooling process via demagnetization, which follows a power law dependence of the magnetic field h : −Δ S ∼ h n . The local exponent n tends to 1 and 2 below and above T C, while has a minimum of 0.648 at T C, which is in accordance with the experimental observation of perovskite manganites Pr0.55 Sr0.45 MnO3 and Nd0.55 Sr0.45 MnO3 (J. Y. Fan et al., Appl. Phys. Lett., 2011, 98, 072508; Europhys. Lett., 2015, 112, 17005) corresponding to the conventional ferromagnets within the mean field theory −Δ S ∼ h 2/3 . At T C, the −Δ S ∼ h curves with a convex curvature superpose each other for small V values, which are separated by the large V case, distinguishing the RKKY interaction and Kondo coupling explicitly. Furthermore, the critical scaling law n ( T C ) = 1 + ( β − 1)/( β + γ ) = 1 + 1/ δ (1 − 1/ β ) is related to the critical exponents ( β, γ, and δ ) extracted from the Arrott–Noakes equation of state and the Kouvel–Fisher method, which fulfill the Widom scaling relation δ = 1 + γβ −1, indicating the self-consistency and reliability of the obtained results. In addition, based on the scaling hypothesis through checking the scaling analysis of magnetization, the M – T – h curves collapse into two independent universal branches below and above T C .