Nature of field-induced transitions and hysteretic magnetoresistance in non-collinear antiferromagnet EuIn2As2

Abstract

We examine the magnetic and electrical transport properties of the hexagonal EuIn2As2 compound, combining experimental and theoretical results. This compound is predicted to be an axion-insulator from an electronic point of view and an altermagnet while in the collinear magnetic phase. However, experiments indicate that the Fermi level lies within the valence band rather than in the topological gap, potentially leading to the dominance of magnetic properties. Our detailed studies on magnetization and electrical transport support the presence of a broken-helix antiferromagnetic state, which was previously identified by X-ray and neutron diffraction experiments. Notably, we observed within that state a field-induced metamagnetic transition marked by a large hysteresis in magnetoresistance, which turns into a sharp upturn for the magnetic field tilted by 15 degree from the c-axis of the crystal. Combined with theoretical calculations, it is explained that the application of a magnetic field changes the low-resistivity antiferromagnetic domain walls to the high-resistivity domain walls due to the reduction in the Fermi surface sheets interaction area in the domain walls, originating from p-orbitals of As. EuIn2As2, therefore, presents a new case study that broadens the understanding of complex magnetic structures and their influence on electrical transport.

Figures (19)

• Figure 1: (a) Temperature-dependent susceptibility ($\chi$) for $\mathbf{B} \perp c$, measured in the zero-field cooled under various magnetic fields. Blue dotted line represents the $\chi$ measured under field cooling for 0.01 and 0.15 T. (b) Zoom portion of (a) for the 0.01 and 0.05 T encompassing two transition temperatures ($T_{N1}$ and $T_{N2}$). (c) $d\chi/dT$ depicts the three transition temperatures: $T_{N1}$, $T_{N2}$, and $T_{MMT}$. Curves are offset for clarity. (d) The real part of the AC susceptibility measured in different DC magnetic fields, $\mathbf{B} \perp c$, with a driving field of 10 Oe and frequency of 299 Hz. (e) Zoom portion of (a) for the 0.05 and 0.08 T encompassing two transition temperatures ($T_{N1}$ and $T_{N2}$). (f) The imaginary part of the ac susceptibility measured in the same DC and AC fields. The arrows represent the transition temperatures $T_{N1}$, $T_{N2}$, and $T_{MMT}$. Data in (d) and (f) are offset by 0.02 and 0.0025 $\text{emu/g}$, respectively.
• Figure 2: (a) Isothermal magnetization measured at several different temperatures in swept-up field (solid line) and swept-down-field (dotted line) regimes. (b) Similar isothermal magnetization in field range 0 - 0.35T. Data at different temperatures in this plot are offset by 0.5$\mu_B$ for clarity. Derivative of magnetization (taken from Fig. \ref{['Figure2']}a) plotted at different temperatures in swept-up-field (c) and swept-down-field (d). The black, red and blue dashed lines represent the $B^\mathrm{up}_1$ (or $B^\mathrm{dn}_1$), $B^\mathrm{up}_2$ (or $B^\mathrm{dn}_2$) and $B^\mathrm{up}_3$ transitions, respectively. (e) The color map of the $\Delta(M) (\equiv M^\mathrm{dn}-M^\mathrm{up})$, where 'dn' and 'up' mark the data collected in the swept-down- and swept-up-field regime, respectively. $T_{N2}$, $T_{N1}$ and $T_{MMT}$ are the transition temperatures extracted from the DC and AC magnetization data, shown in Figs. \ref{['Figure1']}(b-f). $B^\mathrm{up}_1$, $B^\mathrm{up}_2$, $B^\mathrm{up}_3$ and $B^\mathrm{dn}_1$, $B^\mathrm{dn}_2$ are transition fields for swept-up and swept-down fields, respectively, extracted from Fig. \ref{['Figure2']}(c-d).
• Figure 3: (a) Magnetoresistance (MR) measured at different temperatures in swept-up- (solid line) and swept-down-field (dotted line). Data in this plot are offset for clarity. $B^\mathrm{up}_1$, $B^\mathrm{up}_2$, $B^\mathrm{up}_3$ and $B^\mathrm{dn}_1$, $B^\mathrm{dn}_2$ are the same characteristic fields, defined in Fig. \ref{['Figure2']}(c-d). (b) The color map of the $\Delta$MR (= MR$^\mathrm{up}$-MR$^\mathrm{dn}$). (c) MR measured at different angles in swept-up and swept-down. Data are offset by 0.05 for clarity. $B^\mathrm{up}_2$ and $B^\mathrm{dn}_2$ are transition fields for swept-up and swept-down fields, respectively. $B_\mathrm{sat}$ are saturation fields interpolated between values determined for $\textbf{B}\parallel c$ and for $\textbf{B}\perp c$. The inset shows the diagram of MR measurement. (d) The color map of the $\Delta$MR$(B,\theta)$, showing the hysteresis in the MM and fan-type structure states.
• Figure 4: Hall resistivity as a function of magnetic field recorded at various angles for (a) $T$ = 2 K and (b) $T$ = 100 K. Insets to (b) display the angle-dependent carrier concentration at 100 K, respectively. The carrier concentration was estimated using equation \ref{['eqnS2']}.
• Figure 5: (a) The residual Hall resistivity, $\Delta\rho_{yx}$, at 2 K, plotted for different field angles. Data are offset for clarity. (b) Angular dependence of $\rho^A_{yx}$ in a field of 3 T, i.e., above the saturation field. (c) Anomalous Hall conductivity $\sigma^A_{yx}$ plotted against the longitudinal conductivity $\sigma_{xx}$ in a field of 3 T for various angles. The straight violet line is a guide for the eyes, indicating that $\sigma^A_{yx}$ follows the linear relationship with $\sigma_{xx}$. Inset: schematic representation of asymmetric scattering of conduction electrons on the local moments of Eu. (d) The anomalous Hall angle, $\Theta_{AH}$, vs. field orientation angle, $\theta$, in a field of 3 T. Inset shows the diagram of the Hall measurement.