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arXiv · 1407.5689

Pressure-induced giant enhancement of magnetocaloric effects in MnNiSi-based systems

Tapas Samanta·Daniel L. Lepkowski·Ahmad Us Saleheen·Alok Shankar·Joseph Prestigiacomo·Igor Dubenko·Abdiel Quetz·Iain Oswald·Gregory T. McCandless·Julia Y. Chan·Philip W. Adams·David P. Young·Naushad Ali·Shane Stadler
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Abstract

A remarkable decrease of the structural transition temperature of MnNiSi from 1200 K to <300 K by chemically alloying it with MnFeGe results in a coupling of the magnetic and structural transitions, leading to a large magnetocaloric effect near room temperature. It was found that the magnetostructural transition is highly sensitive to external (hydrostatic) pressure: relatively low hydrostatic pressures (~2.4 kbar) lead to an extraordinary enhancement of the isothermal entropy change from $-$Δ$S$ = 44 to 89 J/kg K at ambient (atmospheric) and 2.4 kbar applied pressures, respectively, for a field change of Δ$H$ = 5 T. This giant entropy change is associated with a large relative volume change of about 7% induced by 2.4 kbar applied pressure during the magnetostructural transition. The pressure-enhanced magnetocaloric effects are accompanied by a shift in transition temperature, an effect that may be exploited to tune the transition to the required working temperature, and thereby eliminate the need for a given material to possess a large magnetocaloric effect (i.e., entropy change) over a wide temperature range. Furthermore, this material also possesses negligible hysteresis losses.

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Tapas Samanta, Daniel L. Lepkowski, Ahmad Us Saleheen, Alok Shankar, Joseph Prestigiacomo, Igor Dubenko, Abdiel Quetz, Iain Oswald, Gregory T. McCandless, Julia Y. Chan, Philip W. Adams, David P. Young, Naushad Ali, Shane Stadler. 2014-07-21. Pressure-induced giant enhancement of magnetocaloric effects in MnNiSi-based systems. https://arxiv.org/abs/1407.5689

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