Abstract
The microstructure, magnetic and magnetocaloric properties are investigated in the melt-spun and annealed Ni42.9Co6.9Mn38.3Sn11.9 ribbons. The columnar grains grow perpendicular to ribbon surfaces. After annealing, the grain size increases greatly. Meanwhile, the parent phase is suppressed and therefore L10 martensite predominates, indicating obvious shift of martensitic transformation to high temperature. More interestingly, the martensite variants are distinctly observed on the fractured cross-section of annealed ribbons, not just on the free surface in general. The significant enhancement of magnetic entropy change and effective refrigerant capacities with relatively smaller thermal hysteresis make annealed ribbons potential candidate in magnetic refrigeration around room temperature.
Highlights
Magnetic refrigeration based on the magnetocaloric effect (MCE) is considered as a very promising alternative for the prevailing gas compression-based cooling technology nowadays due to its high cooling efficiency and environmental friendliness.[1,2,3] A lynchpin in making magnetic refrigeration technique possible is to search for materials with good magnetocaloric performance
It is more interesting that the martensite variants are distinctly observed on the fractured cross-section of annealed ribbons, not just on the free surface in general.[23]
It is shown that the A(220) peak almost vanishes, while the M(222) peak predominates, implying that the parent phase is suppressed and the L10 martensite is stabilized.[23]
Summary
Magnetic refrigeration based on the magnetocaloric effect (MCE) is considered as a very promising alternative for the prevailing gas compression-based cooling technology nowadays due to its high cooling efficiency and environmental friendliness.[1,2,3] A lynchpin in making magnetic refrigeration technique possible is to search for materials with good magnetocaloric performance. In 1903, Heusler reported Cu2MnAl and Cu2MnSn alloys, the highly ordered intermetallic compounds with L21 cubic structure and chemical formula of X2YZ (X,Y are the transition metal elements and Z stands for the III-VA main group elements).[4] After that, Ni2MnGa Heusler alloys, known as the ferromagnetic shape memory alloys (FSMAs), has become a hot spot around the world due to the giant magnetic-field-induced strain.[5,6] Compared with the traditional shape memory alloys, the FSMAs show larger strain and higher frequency response.[7] In addition, since the Ni-Mn-Ga FSMAs undergo a first-order martensitic transformation (MT) from high temperature parent phase to low temperature martensite, the excellent magnetofunctional properties such as MCE and magnetoresistance have been achieved due to the abrupt changes of magnetization and resistivity.[8,9]. It is more interesting that the martensite variants are distinctly observed on the fractured cross-section of annealed ribbons, not just on the free surface in general.[23]
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