Anomalous Hall transport in a robust premartensite phase transforming Ni 49 Mn 34 In 16.2 Al 0.8 magnetic shape memory alloy

The interplay of magnetism, structural phase transition, and nontrivial spin texture in magnetic shape memory alloys (MSMAs) offers exciting avenues for exploring exotic physical phenomena and potential applications in spintronic devices. Here, we report the anomalous Hall transport behavior in a robust premartensite (PM)-phase-transforming ${\mathrm{Ni}}_{49}{\mathrm{Mn}}_{34}{\mathrm{In}}_{16.2}{\mathrm{Al}}_{0.8}$ MSMA. Temperature-dependent magnetization data reveal a phase transition from austenite to a robust PM phase at approximately 270 K, further confirmed by temperature-dependent synchrotron x-ray powder diffraction (SXRPD) measurements. The PM phase remains stable over a wide temperature range (270 K down to 100 K), as observed from SXRPD. Anomalous Hall transport measurements performed in both the austenite and PM phases indicate that the anomalous Hall effect originates predominantly from the intrinsic momentum-space Berry curvature. A large topological Hall effect (THE), associated with the real-space Berry curvature, is observed near the PM transition $(\ensuremath{\sim}270\phantom{\rule{0.28em}{0ex}}\mathrm{K})$ and decreases with decreasing temperature. The maximum THE observed at the PM phase boundary suggests the presence of nontrivial spin textures. These findings provide new insights into the coupling between electronic transport, magnetic configurations, and structural transformations in MSMAs, paving the way for the design of materials for spintronic applications.