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• Applying hydrostatic pressure can push the MT to a higher temperature. • Curie transition almost remains unchanged under hydrostatic pressure. • The average magnetic moment and mass susceptibility of SPM cluster are reduced. • The strength of FM/AFM interactions are suppressed by hydrostatic pressure. • The application of hydrostatic pressure suppresses the exchange bias effect. The effect of hydrostatic pressure on martensitic transformation (MT), superparamagnetic (SPM) and exchange bias (EB) behaviors in polycrystalline Ni 45 Cu 5 Mn 35 In 15 has been intensively investigated by various experimental methods. The experimental results show that the studied alloy experiences a MT from the austenitic state with a L 2 1 -type cubic structure to the martensitic state with a seven-layer (7 M) modulated orthorhombic structure with decreasing temperature, accompanied by a significant change in magnetization. It is found that applying hydrostatic pressure can induce the MT to occur in the higher temperature, while the Curie transition almost remains unchanged due to the suppression of ferromagnetic (FM) coupling. In addition, the applied hydrostatic pressure can suppress the EB field and coercivity of the studied alloy due to the reduction of the competition between FM and AFM interactions. This phenomenon can be attributed to the fact that the application of hydrostatic pressure reduces the size of the SPM cluster and its average magnetic moment. [ABSTRACT FROM AUTHOR]

Both the barocaloric effect (BCE) and its reversible behavior during martensitic transformation (MT) have been experimentally investigated in Ni 42.3 Co 7.9 Mn 38.8 Sn 11 quaternary Heusler alloy. The experimental results show that the studied alloy experiences the MT from the ferromagnetic L 2 1 -type cubic structure to the paramagnetic-like three-layered (3 M ) modulated monoclinic structure, resulting in a value of ∼1.1% for the relative volume change ε between two phases. Due to appearance of an enhanced ε , the migration rate of martensitic transformation with respect to the hydrostatic pressure reaches ∼4.7 K/kbar, while a high transition entropy change (∼28 J/kg K) is still maintained. Based on an indirectly estimated method, the calculated maximum value for isothermal entropy change Δ S T achieves ∼ -23 J/kg K with the pressure change of 6.2 kbar, which yields the values of ∼10 K for adiabatic temperature change Δ T a d and ∼786 J/kg for relative cooling power (RCP), performing a large BCE. According to the change of phase fraction at selected hydrostatic pressures, a detailed schematic diagram has been established to evaluate the reversibility of this effect. With applying an external cyclic pressure of 6.2 kbar, the maximum repeatable values calculated for both Δ S T and Δ T a d are decreased to ∼ -15 J/kg K and ∼5 K, respectively. This is attributed to an insufficient driving force, which can only partially transform this material, leading to a reversible MT appeared in the mixed state. [ABSTRACT FROM AUTHOR]

We report effect of hydrostatic pressure on martensitic transformation in polycrystalline Ni 44.6 Co 5.5 Mn 35.5 In 14.4 . With applying pressure, the transformation moves to high temperatures at a rate of 4.4 K/kbar. Utilizing an indirect method, the calculated maximum isothermal entropy changes achieve ~ 14.3 J/kg K at 2.76 kbar and ~ 15.6 J/kg K at 5.98 kbar, which respectively output the values of ~ 5 K and ~ 6 K for the adiabatic temperature change near room temperature. After deducting the average hysteretic loss (~ 152 J/kg), the effective refrigeration capacities still reach ~ 38 J/kg at 2.76 kbar and ~ 247 J/kg at 5.98 kbar, performing an enhanced barocaloric effect. [ABSTRACT FROM AUTHOR]

The evolutions of electrical transport property and Baroresistance (BR) effect at the martensitic transformation (MT) with the change of Co content have been systematically investigated in the Ni 50- x Co x Mn 35 In 15 (0 ≤ x ≤ 7) Heusler system. The structure measurements show that every sample undergoes first-order MT from a L 2 1 cubic structure to a 3 M monoclinic structure. According to magnetic measurements, it is also found that the samples with lower Co content (0 ≤ x ≤ 3) exhibit a paramagnetic MT, i.e. the MT occurs between the paramagnetic austenite and the paramagnetic martensite. At higher Co content, however, the samples display a metamagnetic MT, i.e. the MT occurs between the ferromagnetic austenite and the paramagnetic martensite. Due to the enhancement of the ferromagnetic ordering for the austenitic phase with Co increasing, the difference in resistivity between austenitic and martensitic phases is enlarged significantly. This leads to a giant BR effect with a value of ∼250% associated with the hydrostatic pressure-induced MT can be observed in the sample with x = 6. Moreover, the Hall measurement results indicate that the difference in electrical transport behavior between both phases for the studied alloys mostly relies on the mobility of carriers related to the electro-lattice and the electro-spin scatterings. In this case, the underlying mechanism of the relative contributions originating from these two different scattering processes to the saturated BR effect has been separated quantitively based on the electrical transport measurements under applied different hydrostatic pressures. It demonstrates that the electron-spin scattering acts as a dominant role in improvement of the BR effect for this system. • The MT from a paramagnetic type into a metamagnetic one has been found. • A giant BR effect (∼250%) has been obtained around the room temperature. • The change of electrical transport during MT depends on the mobility of carriers. • Both electro-lattice and electro-spin scatterings has been separated quantitively. • The spin-dependent scattering plays a crucial role to improve the BR effect. [ABSTRACT FROM AUTHOR]