Strong coupling between magnetic order and band topology in the antiferromagnet ${\mathrm{EuMnSb}}_2$

We report a comprehensive magnetization and magnetotransport study on a metallic-type of ${\mathrm{EuMnSb}}_2$ single crystals. A large Hall signal up to room temperature is found in our metallic ${\mathrm{EuMnSb}}_2$, which is dominated by hole carriers with very low carrier density and high mobility. Clear Shubnikov–de Haas oscillations are observed at low temperatures (T $<$ 30 K), from which a dominant tiny hole pocket with small effective mass is deduced. The interplay of carrier density and Mn and Eu moments results in complex magnetic ground states with two successive antiferromagnetic (AFM) transitions appearing at $T_{N1}=24 \mathrm{K}$ and $T_{N2}=9 \mathrm{K}$. In line with the rich magnetic phases, the transport properties, including magnetoresistance, quantum oscillation, and Berry phase, experience abrupt disturbances when crossing the magnetic phase boundaries. The Dirac state is likely quenched once the AFM orders set in, indicating a strong coupling between the AFM magnetic order and the band topology. Our results suggest that metallic-type ${\mathrm{EuMnSb}}_2$ is an ideal platform for the study of the interplay between magnetism, charge transport, and band topology.

Figure 1

(a) Powder x-ray diffraction pattern of ${\mathrm{EuMnSb}}_2$. (b) Temperature dependence of in-plane resistivity ${\rho }_{xx}$ ($x\perp a$) for ${\mathrm{EuMnSb}}_2$ single crystals at 0 and $\pm 9$ T and out-of-plane resistivity ${\rho }_{zz}$ ($z\parallel a$) at 0 T. (c) and (d) Temperature dependence of resistivity for in-plane resistivity at various magnetic fields with the magnetic field applied parallel (c) and perpendicular (d) to the $a$ axis. (c) and (d) use the same legend. (e) Temperature dependence of specific heat for ${\mathrm{EuMnSb}}_2$. The red line represents the fit using the Debye-Einstein model. The inset shows the magnetic contribution to the specific heat $\mathrm{\Delta }{C}_p/T$ = ($C_p-C_{\text{ph}+\text{el}})/T$. (f) Low-temperature specific heat in various magnetic fields. Arrows in (c)–(f) mark the magnetic transitions.

Figure 2

(a) The crystal and magnetic structure of ${\mathrm{EuMnSb}}_2$ ($1\times 3\times 3$ unit cells). Mn sublattices exhibit a C-type AFM order below $T_N\sim$ 350 K. Eu sublattices exhibit a canted A-type AFM order below $T_{N1}=$ 24 K with spins lying in the $ac$ plane; different orientations correspond to different magnetic phases, which depend on the specific temperature and magnetic field. (b) Temperature dependence of magnetic susceptibility $\chi$ (left $y$ axis) and its inverse ${\chi }^{-1}$ (right $y$ axis) for an ${\mathrm{EuMnSb}}_2$ single crystal with $B\parallel a$ and $B\perp a$ and $B$ = 1 T. Red lines represent the Curie-Weiss fit. (c) and (d) Temperature (c) and magnetic field (d) dependence of the magnetization for $M_{\parallel }$ (closed squares) and $M_{\perp }$ (open circles), respectively. Each subsequent magnetization set in (d) is shifted upward by 1 ${\mu }_B$/f.u. for clarity. (e) and (f) Magnetic phase diagrams of ${\mathrm{EuMnSb}}_2$ for $B\parallel a$ (e) and $B\perp a$ (f), respectively. The color maps represent $d\chi /dT$ in the parameter spaces of temperature and magnetic field.

Figure 3

(a) Magnetic field dependence of MR at various temperatures with $B\parallel a$. (b) Log-log plot of MR vs magnetic field to highlight the power law of $\mathrm{MR}(B$). (c) Kohler plot in a log-log scale for ${\mathrm{EuMnSb}}_2$. (d) Temperature dependence of the fitting parameter $n$ in MR = $A{B}^n$. (e) Magnetic field dependence of MR with different tilt angles at $T$ = 2 K. (f) MR vs tilt angle at different magnetic fields at 2 K. The red line is the fit using the 2D model. (g) Magnetic field dependence of Hall resistivity ${\rho }_{xy}$ at different temperatures with $B\parallel a$. (h) Temperature dependence of carrier concentration $n_h$ inferred from the single-band fitting. (a)–(c) and (g) use the same legend, which is shown in (a).

Figure 4

(a) Contour plot of $d\rho /dB$ calculated from Fig. 3 as a function of temperature $T$ and magnetic field $B\parallel a$. Magnetic transitions are also plotted to compare with $d\rho /dB$; solid and dashed lines are guides to the eye. (b) SdH oscillatory components $\mathrm{\Delta }\rho$ at different temperatures obtained by subtracting the smooth polynomial background. (c) FFT spectra for the SdH oscillations in (b). (d) Temperature of the oscillation amplitude (Osc. Amp.) at $F_{\beta }$. (e) Fitting of SdH oscillation at 1.6 K using the LK formula. (f) Phase factor $\gamma$ of SdH oscillation as a function of temperature.