Modeling specific heatandentropychangeinLa(Fe-Mn-Si)13-H compounds

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:400

Article; Proceedings Paper

Piazzi, Marco¹  Bennati, Cecilia^1,2  Curcio, Carmen^1,2  Kuepferling, Michaela¹  Basso, Vittorio¹ 

[1] Ist Nazl Ric Metrol, I-10135 Turin, Italy

[2] Politecn Torino, DISAT, I-10129 Turin, Italy

关键词: Magnetocaloric effect;    Entropychange;    Mean field theory;    Magnetoelastic coupling;   

DOI  :  10.1016/j.jmmm.2015.07.055

来源: Elsevier

【 摘 要 】

In this paper we model the magnetocaloric effect of LaFexMnySiz-H-165 compound (x + y + z = 13), a system showing a transition temperature finely tunable around room temperature by Mn substitution. The thermodynamic model takes into account the coupling between magnetism and specific volume as introduced by Bean and Rodbell. We find a good qualitative agreement between experimental and modeled entropy change -Delta s (H, T). The main result is that the magnetoelastic coupling drives the phase transition of the system, changing it from second to first order by varying a model parameter eta. It is also responsible for a decrease of -Delta s at the transition, due to a small lattice contribution to the entropy counteracting the effect of the magnetic one. The role of Mn is reflected exclusively in a decrease of the strength of the exchange interaction, while the value of the coefficient beta, responsible for the coupling between volume and exchange energy, is independent on the Mn content and it appears to be an intrinsic property of the La(Fe-Si)13 structure. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

Free