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TT: Fachverband Tiefe Temperaturen

TT 38: Magnetocaloric Effects (joint session MA/TT)

TT 38.5: Vortrag

Dienstag, 13. März 2018, 10:30–10:45, EB 407

Decoupling of the magnetostructural transition in magntocaloric La-Fe-Si alloys — •Yanyan Shao^1,2, Konstantin Skokov², Francois Guillou³, Dmitriy Yu Karpenkov², Mingxiao Zhang¹, Oliver Gutfleisch², and Jian Liu¹ — ¹Ningbo Institute of Material Technology and Engineering, CAS, 315201 Ningbo, China — ²Material Science, TU Darmstadt, 64287 Darmstadt, Germany — ³European Synchrotron Radiation Facility, 38000 Grenoble, France

The giant magnetocaloric effect occurs when a magnetic material undergoes a first-order magnetic transition, which usually involves the coupling of magnetic and lattice contributions [1]. In order to investigate in detail the evolution of the magnetostructural phase transition, both magnetocaloric (dT(H)) and magnetovolume (dV(H)) effects in La1.7Fe11.6Si1.4 alloy were measured simultaneously. We observed that under isothermal conditions, only heat transfer occurs first, whereas the structural transition takes place in higher fields, where the heat transfer is already in progress or almost completed. The shift between the magnetic and structural transitions is 0.27 T, which clearly indicates a decoupling effect. The decoupling effect was also confirmed by X-ray absorption (lattice contribution) and by magnetic circular dichroism (change in magnetic system). We will discuss different reasons for the decoupling effect. [1]V. K. Pecharsky et al., Physical Review Letters. 91 (2003) 197204.