Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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Influence of the martensitic transformation kinetics on the magnetocaloric effect in Ni-Mn-In
The inverse magnetocaloric effect in Ni-Mn based Heusler compounds occurs during the magnetostructural transition between low-temperature, low-magnetization martensite and high-temperature, high-magnetization austenite. In this study, we analyze the metamagnetic transformation of a Ni49.8Mn35In15.2 compound by simultaneous adiabatic temperature change ΔTad and strain Δl/l0 measurements in pulsed magnetic fields up to 10 T. We observe a ΔTad of −10 K and a Δl/l0 of −0.22% when the reverse martensitic transition is fully induced at a starting temperature of 285 K. By a variation of the magnetic field-sweep rates between 316, 865, and 1850 T s−1, the transitional dynamics of the reverse martensitic transformation have been investigated. Our experiments reveal an apparent delay upon the end of the reverse martensitic transformation at field rates exceeding 865 T s−1 which is related to the annihilation of retained martensite. As a consequence, the field hysteresis increases and higher fields are required to saturate the transition. In contrast, no time-dependent effects on the onset of the reverse martensitic transformation were observed in the studied field-sweep range. Our results demonstrate that kinetic effects in Heusler compounds strongly affect the magnetic cooling cycle, especially when utilizing a multicaloric “exploiting-hysteresis cycle” where high magnetic field-sweep rates are employed.
Physical Review Materials 4(2020), 111401(R)