Negative Magnetoresistance in Nanotwinned NiMnGa Epitaxial Films

Abstract

Magnetic shape memory alloys are under intensive investigation due to their unusual physical properties, such as magnetic shape memory effect, magnetic field induced superelasticity, direct and inverse magnetocaloric effect etc., promising for novel applications. One of the intriguing properties of these materials in a single phase state is a giant magnetoresistance. Here we report the remarkable results about the magnetoresistive properties of epitaxial films of Ni52.3Mn26.8Ga20.9 magnetic shape memory alloy in the temperature range of 100–370 K, well below the martensitic transformation temperature. It was found that the formation of non-collinear magnetic structure due to a nanotwinning of the film results in electron scattering on such a structure and noticeable negative magnetoresistance in the entire investigated temperature range.

Anomalous Hall effect in Ni47.3Mn30.6Ga22.1/MgO(001)Blinov1, Chernenko2, Прудников3 et al. 2020Phys. Rev. BSelf Cite2000View full textAdd to dashboardCite

“…By applying a magnetic field, however, the non-collinear structures disappear. In addition, the non-collinear structures are more pronounced at low temperatures and tend to disappear gradually with the increase of temperature [24]. As can be seen in Fig.…”

“…It is well known that an excess of Mn in the atomically ordered MSMAs, as in our case, gives rise to antiferromagnetic (AF) interactions between Mn atoms on their proper sites and those on the Ga sites [27,28]. Such AF interactions compete with the ferromagnetic interactions between Mn magnetic moments on their proper sites, and lead to non-collinear magnetic structures [24]. By applying a magnetic field, however, the non-collinear structures disappear.…”

“…Figure 3 shows the temperature dependence of MR between 100 and 400 K. Figure 3 shows that MR is negative and small, less than 1% at 20.5 kOe, which is typical for Ni-Mn-Ga alloys [24][25][26]. MT has a weak influence on MR, since the resistivity itself (Fig.…”

“…The behavior of resistivity, (T), in the vicinity of MT is typical of Ni-Mn-Ga alloys [21,24,25]. With increasing temperature, the resistivity increases in the martensitic phase, then decreases in the MT region and monotonically increases in the austenitic phase.…”

Effect of Cu Doping on Phase Transition, Thermal Strain, and Thermal Expansion Property in Polycrystalline Ni50Mn23−xCuxGa27 Alloys

“…Ni-Mn-Ga alloys are new kinds of ferromagnetic shape memory alloys that exhibit shape memory effect (SME). [1,2] In recent years, some other important effects, including a variety of different caloric effects (magnetocaloric, [3][4][5] barocaloric, [6,7] and elastocaloric), [8,9] magnetoresistance effect, [10,11] and negative thermal expansion (NTE) effect, [12] have been found in Ni-Mn-Ga alloys. Due to their multifunctionality, Ni-Mn-Ga alloys have always been the focus of researchers all over the world.…”