Uniaxial stress tuning of the anomalous Hall effect in Mn3Ge

TL;DR

This work demonstrates that uniaxial stress can selectively tune the anomalous Hall effect in Mn3Ge by distorting in-plane spin configurations within the kagome lattice. Using high-energy X-ray diffraction and transport measurements under controlled uniaxial loading, the authors show that in-plane stress linearly modifies the c/a ratio and dramatically alters the AHE, whereas out-of-plane stress has minimal impact due to elastic anisotropy. The AHE response under uniaxial in-plane strain differs from hydrostatic pressure, which reverses the AHE by promoting out-of-plane spin canting, indicating different magnetic reorientation pathways. The findings highlight strain engineering as a precise tool to manipulate Berry-curvature–driven transport in kagome magnets, with potential applications in spintronic sensors and memory devices.

Abstract

Tunable electronic properties in magnetic materials lead to novel physical phenomena that have the potential to be exploited in the design of new spintronic devices. Here, we report the effect of uniaxial stress on the anomalous Hall effect (AHE) in the hexagonal frustrated antiferromagnetic Heusler compound Mn3Ge. Our x-ray diffraction results show that the c/a ratio varies linearly with strain when stress is applied along the a axis, as well as a significantly higher Young's modulus along the c direction. The linear behavior of the c/a ratio under uniaxial stress mirrors that seen under hydrostatic pressure up to 1.8 GPa, but results in a characteristically different behavior of the AHE. Stress applied along the a axis induces a distortion in the ab plane, smoothing the abrupt jump in the AHE signal at zero magnetic field. In contrast, stress applied along the c axis has little effect, presumably due to the higher Young's modulus. We argue that this is due to pronounced changes in magnetic order.

Figures (6)

• Figure 1: Real space structures of Mn$_3$Ge illustrating two experiments with stress applied along different directions: (a) Stress was applied along the $[2~\overline{1}~\overline{1}~0]$ direction, i.e., along $[1~0~\overline{1}~0]$ ($x$ direction) in real space. The magnetic field was applied perpendicular to the $x$ axis, in the $y$ direction, aligned with the $[0~1~\overline{1}~0]$. Finally, the Hall voltage ($V_{xz}$) was measured along the $[0~0~0~1]$ direction, referred to as the $z$ axis in real space. The second configuration is obtained by performing two successive counterclockwise $90^{\circ}$ rotations on the real lattice. First a rotation around the $y$ axis, followed by a second rotation around the $z$ axis. (b) Stress was then applied along the $z$ axis while the magnetic field was directed along the $x$ axis. Hall voltage ($V_{zy}$) was measured along the $y$ axis.
• Figure 2: XRD results under applied stress along the $a$ direction are compared with hydrostatic pressure data extracted from sukhanov2018gradual, both at 300 K. The right axis of the plot (red spheres) shows the relative strain along $a$, $\varepsilon_a$, as a function of the lattice parameter ratio $c/a$, where zero strain corresponds to the nominal experimental value. The left axis (blue spheres) represents the applied hydrostatic pressure as a function of $c/a$. The "X" marks the point at which the AHE is suppressed under hydrostatic pressure. The inset shows the variation of the interplanar planes $d_{01\overline{1}0}$, corresponding to $b^*$, and $d_{0001}$, corresponding to the lattice parameter $c$, as a function of strain under stress applied along the $a$ direction. The step size is the same for the left and right axes.
• Figure 3: Hall resistivity $\rho_{zy}$ of Mn$_3$Ge under compressive stress applied along the $z$ axis at (a) 10 K and (b) 200 K. The field was applied along the $y$ axis and the data was recorded with an increasing magnetic field. The zero strain curves were measured separately outside of the strain cell.
• Figure 4: Hall resistivity $\rho_{xz}$ of Mn$_3$Ge under compressive stress applied along the $x$ axis at (a) 10 K and (b) 200 K. The magnetic field was applied along the $y$ direction and the data was recorded with an increasing magnetic field. The zero strain curve at 10 K was measured separately outside of the strain cell. The insets display the positions of the step-like features observed at low magnetic fields as a function of compressive strain. The dotted lines serve as a guide to the eye.
• Figure 5: (a) Magnetic structure of Mn$_3$Ge for a magnetic field applied along the $[0~1~\overline{1}~0]$ direction. The black and green arrows represent the anti-chiral antiferromagnetic structure. When the field direction is reversed, the spins flip $180^{\circ}$kiyohara2016giant. The green arrows correspond to the moments aligned with the local easy axis dasgupta2020theory. (b) Stress induces an additional easy axis along the stress application that induces the spins to rotate towards such axis.