Research ArticleCONDENSED MATTER PHYSICS

Large anomalous Hall effect driven by a nonvanishing Berry curvature in the noncolinear antiferromagnet Mn3Ge

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Science Advances  15 Apr 2016:
Vol. 2, no. 4, e1501870
DOI: 10.1126/sciadv.1501870
  • Fig. 1 Crystal structure, magnetic structure, and Berry curvature of Mn3Ge.

    (A) Crystal structure showing the two layers of Mn-Ge atoms stacked along the c(z) axis. Red and blue spheres represent atoms lying in the z = 0 and z = c/2 planes, respectively. Large and small spheres represent Mn and Ge atoms, respectively. In each layer, the Mn atoms form a Kagome-type lattice. (B) Calculated 120° antiferromagnetic configuration in the z = 0 and z = c/2 planes, respectively. Only the Mn atoms are shown, with their moments represented by arrows. The green dashed line indicates the mirror plane (that is, the xz plane). Corresponding mirror reflection plus a translation by c/2 along the z axis transforms the system back into itself, by exchanging two magnetic planes. (C) First Brillouin zone and momentum-dependent AHC. The mirror plane (that is, kxkz plane) is highlighted in green. The component of the AHC tensor (Embedded Image) is shown in the kikj plane, which corresponds to the Berry curvature of all occupied electronic states integrated over the kk direction. Here, only the Embedded Image component exhibits large values. (D) Illustration of the rotation of the triangular spin structure with an in-plane field. There is a small in-plane net magnetic moment that we calculate to be along the direction indicated. When the field (H) rotates by 180°, the chiral spin structure can be reversed, resulting in the sign change in the AHC.

  • Fig. 2 AHE.

    (A to F) Hall resistivity (ρH) (A, C, and E) and Hall conductivity (σH) (B, D, and F) as a function of magnetic field (H), measured at four representative temperatures between 2 and 300 K, for three different current and magnetic field configurations. The hexagon in the inset to (C) and (D) shows the two in-plane directions used for the current and magnetic field in the present measurements.

  • Fig. 3 Magnetic properties.

    Field dependence of magnetization M (H) measured at 2 K, with the field parallel to the three orientations used in the AHE measurements. The inset shows M (H) loops measured at 300 K.

  • Fig. 4 Angular dependence of AHE.

    Angular (θ) dependence of the AHC measured for the three current and field configurations used in Fig. 2. A schematic diagram of the sample geometry is shown for each configuration. (A to C) The rotation was performed along (A) y-z for I along z [0001], (B) x-z for I along y [01-10], and (C) y-z for I along x [2-1-10]. θ = 0 corresponds to H oriented along y, x, and z in (A), (B), and (C), respectively. We have used the same x, y, z coordinates as shown in the theoretical spin arrangement in Fig. 1B.

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Temperature dependence of magnetization.
    • fig. S2. Conductivity with temperature.

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