Abstract
High magnetocaloric refrigeration performance requires large magnetic entropy change ΔSM and broad working temperature span ΔTFWHM. A fourth element doping of Co in ternary Ni-Mn-Sn alloy may significantly enhance the saturation magnetization of the alloy and thus enhance the ΔSM. Here, the effects of Co-doping on the martensite transformation, magnetic properties and magnetocaloric effects (MCE) of quaternary Ni47−xMn43Sn10Cox (x = 0, 6, 11) alloys were investigated. The martensite transformation temperatures decrease while austenite Curie point increases with Co content increasing to x = 6 and 11, thus broadening the temperature window for a high magnetization austenite (13.5, 91.7 and 109.1 A·m2/kg for x = 0, 6 and 11, respectively). Two successive magnetostructural transformations (A → 10 M and A → 10 M + 6 M) occur in the alloy x = 6, which are responsible for the giant magnetic entropy change ΔSM = 29.5 J/kg·K, wide working temperature span ΔTFWHM = 14 K and large effective refrigeration capacity RCeff = 232 J/kg under a magnetic field of 5.0 T. These results suggest that Ni40.6Mn43.3Sn10.0Co6.1 alloy may act as a potential solid-state magnetic refrigerant working at room temperature.
Highlights
IntroductionRare earth containing low temperature magnetic refrigeration compounds, such as TbMn2Si236, ErGa37, DyB238, HoPdIn39, may exhibit a two successive magnetic transitions behavior deriving from the coupling of spin-reorientation temperature (TSR) and Curie temperature (Tc); Two successive ΔSM peaks with the same sign, associated with a first-order martensite transformation (MT) and an intermediate martensite transformation (IMT), have been discovered in some Ni-Mn-X alloys after composition tuning or under external pressure[40,41,42]
Over the last decade, Ni-Mn-X (X = Sn, In and Sb) metamagnetic shape memory alloys (MSMAs) have attracted significant interests due to their potential applications as magnetic refrigeration materials near room temperature
Enhanced ΔM is in favor of large Ezeeman, which is responsible for the high magnetic entropy change (ΔSM) and wide working temperature span (ΔTFWHM, defined as the full width at half maximum of the magnetic entropy peak)[8], where the ΔTFWHM is crucial for magnetic refrigeration applications in the case of inverse MCE9,10
Summary
Rare earth containing low temperature magnetic refrigeration compounds, such as TbMn2Si236, ErGa37, DyB238, HoPdIn39, may exhibit a two successive magnetic transitions behavior deriving from the coupling of spin-reorientation temperature (TSR) and Curie temperature (Tc); Two successive ΔSM peaks with the same sign, associated with a first-order martensite transformation (MT) and an intermediate martensite transformation (IMT), have been discovered in some Ni-Mn-X alloys after composition tuning or under external pressure[40,41,42] These two adjacent transformations lead to a partially overlap of the refrigerant temperature intervals, yielding an improved refrigerating capacity. A large magnetic entropy change ΔSM of 29.5 J/kg·K with a wide ΔTFWHM of ~14 K attributed to the occurrence of successive magnetostructural transformations and a strong metamagnetic transition behavior were revealed in the Co6 alloy
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