Investigations on the electronic transport and piezoresistivity properties of Ni2−XMn1+XGa (X = 0 and 0.15) Heusler alloys under hydrostatic pressure

Abstract

The resisitivity of Ni2−XMn1+XGa (X = 0 and 0.15) magnetic shape memory alloys has been investigated as a function of temperature (4–300 K) and hydrostatic pressure up to 30 kilobars. The resistivity is suppressed (X = 0) and enhanced (X = 0.15) with increasing pressure. A change in piezoresistivity with respect to pressure and temperature is observed. The negative and positive piezoresistivity increases with pressure for both the alloys. The residual resistivity and electron-electron scattering factor as a function of pressure reveal that for Ni2MnGa the electron-electron scattering is predominant, while the X = 0.15 specimen is dominated by the electron-magnon scattering. The value of electron-electron scattering factor is positive for both the samples, and it is decreasing (negative trend) for Ni2MnGa and increasing (positive trend) for X = 0.15 with pressure. The martensite transition temperature is found to be increased with the application of external pressure for both samples.

High-resolution synchrotron x-ray powder diffraction study of the incommensurate modulation in the martensite phase ofNi2MnGa: Evidence for nearly 7M modulation and phason broadening

“…We also compare the simulated single crystal diffraction patterns of the incommensurate phase using first, second and third order satellites to confirm unambiguously that the structure of Ni 2 MnGa is 7M like, although incommensurate. The present results also indicate that the incommensurate modulation in stoichiometric Ni 2 MnGa cannot originate from the adaptive phase model [1] in view of the (1) significant mismatch between the calculated and observed peak positions of the superlattice reflections using commensurate 7M modulation, ( 2 resistivity measurement [29] are consistent with T PM and T M reported by other workers for stoichiometric Ni 2 MnGa [16] The initial characterization results are given in Ref. [14].…”

Enhanced magnetocaloric performances and tunable martensitic transformation in Ni35Co15Mn35−xFexTi15 all-d-metal Heusler alloys by chemical and physical pressures

“…On the one hand, T t (T t ʹ) listed in Table S1, 196 K (234 K) for P = 0.25 GPa, 200 K (246 K) for P = 0.35 GPa, 236 K (262 K) for P = 0.72 GPa, monotonically increases with increasing applied hydrostatic pressure, meaning that the hydrostatic pressure stabilizes the martensite due to the fact that the unit cell volume in the martensitic state is lower than that in the austenitic state [41]. Strengthening of d-d hybridization results in more thermodynamic driving force needed to make the MT occur [36,44]. On the other hand, the value of ΔM increases first at 0.25 GPa resulting from enhancement of FM interaction of Mn(B)-Co(A)-Mn(D) configuration.…”

“…Meanwhile, the first principle calculations were also used to predict the stability of phase, possible martensitic transformation (MT), and electronic behaviors [29][30][31][32] for other similar alloys in all-d-metal Heusler systems. Moreover, the hydrostatic pressure is considered as a clean way to affect the atomic distance and thus change the physical properties of the materials, especially for some MST systems [33][34][35][36][37][38]. Furthermore, dual-field-induced change of physical performances has also been studied.…”

The effect of Mn on structural, magnetic and magnetoresistance properties of Ni–Mn–Sb Heusler melt spun ribbons under extreme conditions

“…Magnetocaloric materials, which have a maximum entropy change value close to room temperature (RT), have attracted much attention during the past two decades because of their advantages in terms of compact size, energy efficiency, and environmental friendliness for refrigeration applications [1,2]. Up to now, considerable research has been done on a number of materials having first-order magnetic phase (FOST) transitions, including La(Fe,Si) 13 , NiMnGa, Gd 5 (Si,Ge) 4 , Co 2 NiGa, MnFeP 1 − y As y , and CoNiAl [3][4][5][6][7][8][9][10].…”