Relative contributions of the electron-lattice and the electron-spin scatterings to the giant baroresistance effect in Ni–Co–Mn–In system

Highlights: • 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: 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-xCo_xMn₃₅In₁₅ (0 ≤ x ≤ 7) Heusler system. The structure measurements show that every sample undergoes first-order MT from a L2₁ 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.