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High-performance magnetocaloric materials should have a large reversible magnetocaloric effect and good heat exchange capability. Here, we developed a Ni48.1Co2.9Mn35.0In14.0 metamagnetic shape memory microwire with a large and reversible inverse magnetocaloric effect. As compared to the bulk counterpart, the microwire shows a better combination of magnetostructural transformation parameters (magnetization difference across transformation ΔM, transformation entropy change ΔStr, thermal hysteresis ΔThys, and transformation interval ΔTint) and thus greatly reduced critical field required for complete and reversible magnetic-field-induced transformation. A strong and reversible metamagnetic transition occurred in the microwire, which facilitates the achievement of large reversible magnetoresponsive effects. Consequently, a large and reversible magnetic-field-induced entropy change ΔSm of 12.8 J kg-11K-1 under 5 T was achieved in the microwire, which is the highest value reported heretofore in Ni-Mn-based magnetic shape memory wires. Furthermore, since microwires have a high surface/volume ratio, they exhibit very good heat exchange capability. The present Ni48.1Co2.9Mn35.0In14.0 microwire shows great potential for magnetic refrigeration. This study may stimulate further development of high-performance magnetocaloric wires for high-efficiency and environmentally friendly solid-state cooling. [ABSTRACT FROM AUTHOR]

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Superelastic behavior is traditionally related to the martensitic transition with a collective transformation scenario in some shape memory alloys. A kind of quasi-linear superelasticity accompanied by a finite avalanche or confined martensitic transformation was recently found in some alloy systems with strain glass state. Here, an in situ neutron diffraction technique was used to study the deformation behavior in an Ni43Fe18Ga27Co12 alloy with strain glass state in order to reveal the new intrinsic physical nature of the quasi-linear superelasticity. A significant modulus softening prior to the stress-induced martensitic transformation was observed during compression in the studied alloy, which is similar to the characteristics exhibited in the tweed precursor phenomena prior to temperature-induced martensitic transformation. Moreover, the diffraction peak broadening was further shown during the elastic stage of deformation for both single-crystal and polycrystalline samples, which mainly stems from the short-range fluctuation in the strain field inside each grain based on Williamson-Hall analysis. The authors believe that there exists a spatial heterogeneity in the modulus of the confined martensitic transformation alloy. [ABSTRACT FROM AUTHOR]

We report a giant effective magnetic refrigeration capacity in a Ni40Co10Mn40Sn10 multifunctional alloy. With a large magnetization difference between austenite and martensite, this alloy shows a strong magnetic field dependence of transformation temperatures. Complete magnetic-fieldinduced structural transformation and a considerable magnetic entropy change are observed in a broad operating temperature window of 33K near room temperature. Consequently, an effective magnetic refrigeration capacity of 251 J/kg for 5 T is achieved, which is the largest value for Ni-Mn-based Heusler alloys and comparable to that of the high-performance Gd-Si-Ge and La-Fe-Si magnetocaloric materials. Incorporating the advantages of low cost and non-toxicity, this alloy shows very promising prospects for room-temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

A ferromagnetic shape memory alloy of Ni48Mn30Ga22 prepared by induction melting was successfully hot forged. Strong textures and a large anisotropy of in plane plastic flow were developed during the hot forging process. The crystal structures, both in austenitic and martensitic states, were investigated by means of neutron powder diffraction technique. The result suggests that Ni48Mn30Ga22 has a cubic L21 Heusler structure at room temperature, the same as that in the stoichiometric Ni2MnGa. When cooled to 243 K, the Ni48Mn30Ga22 alloy changes into a seven layered orthorhombic martensitic structure. No substantial change of the neutron diffraction pattern was observed upon further cooling to 19 K, indicating that there is no intermartensitic transformation in the investigated alloy, which is different from the transformation processes in the Ni–Mn–Ga alloys with higher martensitic transformation temperatures. [ABSTRACT FROM AUTHOR]

The magnetic state of the low-temperature martensite in a Ni43.5Co6.5Mn39Sn11 magnetic shape memory alloy (MSMA) is disclosed. At temperatures (T) above a critical temperature Tf, the magnetization versus field [M(H)] curves display a sigmoid shape, show no magnetic hysteresis, and can be well fitted according to the Langevin model, confirming that the martensite shows superparamagnetic behavior at T>Tf. On the other hand, the observation of a memory effect during the stop-and-wait protocol and the analysis of dynamic magnetic properties probed by ac susceptibility measurements unequivocally corroborate the superspin glass behavior of interacting magnetic clusters at T

Dynamic measurements of the Henry factor αH of InAs/GaAs Fabry-Pérot lasers are compared for 3-, 5- and 10-QD layers. While αH dramatically increases with the bias current for 3- and 5-QD stacks, it only amounts to <4 for the 10-layer stack at high currents, a value similar to that of QW-lasers. [ABSTRACT FROM AUTHOR]

The crystal structures, magnetic structures, and phase transformation of the off-stoichiometric Ni53Mn25Ga22 were studied by neutron powder diffraction at different temperatures. It is shown that Ni53Mn25Ga22 has a tetragonal I4/mmm structure from 20 K to 403 K. An abrupt jump in unit-cell volume around room temperature, corresponding to an endothermic peak in the differential scanning calorimetry curve, was observed. This indicates a pretransformation in the martensitic phase of Ni53Mn25Ga22, which is completely different from the phase transformation in the stoichiometric Ni2MnGa. The sequence of structural transformation in Ni53Mn25Ga22 is closely related to its intrinsic temperature-dependent magnetic structure. [ABSTRACT FROM AUTHOR]