邀请人：王晶 副研究员、胡凤霞 研究员

报告摘要
A critical requirement for the application of magnetocaloric materials in magnetic refrigeration technology is not only the magnitude of the effect but also its stability under cyclic application of magnetic fields. This paper presents a detailed experimental study and analysis of the reversibility of the adiabatic temperature change (ΔTad) in the Ni36.5Co13.5Mn35Ti15 Heusler alloy, which exhibits a magnetostructural phase transition (MSPT). Direct measurements of ΔTad were performed under both single and cyclic magnetic field exposure (1.8 T and 8 T) for the direct (austenite → martensite) and reverse (martensite → austenite) martensitic phase transitions. An asymmetry in the cyclic stability of ΔTad was revealed. During the martensite→austenite phase transition, irreversible degradation of ∆Tad is observed due to the presence of a metastable martensite phase. The maximum value of the inverse magnetocaloric effect (IMCE) of a single switch-on is -11.2 K at T=313 K, and the value of the stable IMCE is -9 K at T=310 K. During the austenite→martensite phase transition, the effect is completely reversible and stable in cyclic magnetic fields of both 1.8 and 8 T, with the maximum stable IMCE value of -7.5 K. It is shown that for the reversible IMCE, ΔTad depends quadratically on the magnetic field (ΔTad∼H2). Analysis of the influence of cyclic exposure to fields of 2, 4, and 8 T at T=312 K showed that there is a certain stable value to which the effect tends during cycling in a magnetic field, regardless of the magnitude of the first-switch-on effect. The results of this work reveal the nature of the irreversibility of the MCE in Heusler alloys and indicate that magnetic cooling cycles based on direct martensitic transition can exhibit exceptional stability over a wide temperature range, making this alloy a promising candidate for reliable solid-state cooling technology.

简历
Dr.Adler Gamzatovisa, Leading Researcherat Laboratory of Low Temperature Physics & Magnetism, Amirkhanov Institute of Physics of Dagestan Federal Research Center of Russian, Academy of Science. He received his PhD from Amirkhanov Institute of Physics of Dagestan Scientific Center of Russian Academy of Science in 2011.Current research activities include Experimental study of thermal (specific heat, thermal conductivity, thermal diffusion), magnetotransport properties (resistivity, magnetoresistance) and magnetocaloric properties of the new magneticmaterials (manganites, multiferroics, Heusleralloys et.al.). He has published about 100 scientific papers in journals Applied Physics Letters, ACS Appl. Mater. Interfaces, Journal of Alloys and Compounds, Intermetallics, Journal of Materials Science, J. Phys D.,etc.