Pressure tuning of the anomalous Hall effect in the chiral antiferromagnet ${\mathrm{Mn}}_3\mathrm{Ge}$

We report on the pressure evolution of the giant anomalous Hall effect (AHE) in the chiral antiferromagnet ${\mathrm{Mn}}_3\mathrm{Ge}$. The AHE originating from the nonvanishing Berry curvature in ${\mathrm{Mn}}_3\mathrm{Ge}$ can be continuously tuned by application of hydrostatic pressure. At room temperature, the Hall signal changes sign as a function of pressure and vanishes completely at $p=1.53\mathrm{GPa}$. Even though the Hall conductivity changes sign upon increasing pressure, the room-temperature saturation value of $23{\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$ at 2.85 GPa is remarkably high and comparable to the saturation value at ambient pressure of about $40{\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$. The change in the Hall conductivity can be directly linked to a gradual change of the size of the in-plane components of the Mn moments in the noncollinear triangular magnetic structure. Our findings, therefore, provide a route for tuning of the AHE in the chiral antiferromagnetic ${\mathrm{Mn}}_3\mathrm{Ge}$.

Figure 1

(a) Illustration of the rotation of the triangular spin structure upon application of an in-plane magnetic field. The direction of in-plane net magnetic moment is represented by the gray arrow. (b) Schematic drawing of the sample device for the electrical-transport measurements used inside the pressure cell.

Figure 2

(a) and (b) Hall resistivity (${\rho }_{yz}$) and Hall conductivity (${\sigma }_{yz}$) as a function of magnetic field ($H$) at representative temperatures between 5 and 300 K for pressures of 0.05 and 2.85 GPa, respectively.

Figure 3

Field dependence Hall conductivity for ${\mathrm{Mn}}_3\mathrm{Ge}$ at room temperature for selected pressures.

Figure 4

(a) The inverse triangular magnetic structure of ${\mathrm{Mn}}_3\mathrm{Ge}$ at ambient pressure (top) and at $p=2.85\mathrm{GPa}$ (bottom). (b) Pressure-temperature color map of the AHE amplitude ($\mathrm{\Delta }{\rho }_{\mathrm{yz}}$) for the ${\mathrm{Mn}}_3\mathrm{Ge}$ compound. The bullets represent the angle of the spin moments out of the (0001) plane extracted from previous neutron diffraction experiments [20, 21]. The gray dashed line indicates a vanishing AHE.