Field-induced magnetic phase transitions and transport anomalies in GdAlSi

TL;DR

GdAlSi, a noncentrosymmetric member of the RAlX family, is proposed as a magnetic Weyl semimetal where 4f ordering breaks time-reversal symmetry. The study synthesizes high-quality GdAlSi single crystals and performs comprehensive magnetization, resistivity, Hall, and specific heat measurements to map magnetic transitions under temperature and magnetic field, with $B$ applied along the $c$ axis. It uncovers two zero-field antiferromagnetic transitions at $T_{N1}\approx 31.9$ K and $T_{N2}\approx 31.1$ K and reveals a field-induced transition at $T_{N3}$ above $8$ T, producing a dendritic $B$–$T$ phase diagram with metamagnetic features at $B_1$, $B_2$, etc. The transport data show step-like magnetoresistance, hysteresis, and Hall anomalies tied to magnetic-order reconstruction, while magnetization changes are subtle, consistent with a non-collinear, possibly cycloidal spin texture stabilized by Dzyaloshinskii–Moriya interactions. Overall, the work demonstrates tunable magnetic and transport phenomena in GdAlSi, highlighting its potential to realize correlated topological states and to engineer magnetic-phase-driven topological transitions in Weyl semimetals.

Abstract

Magnetic topological materials hosting non-zero Berry curvature have emerged as a focus of intensive research due to their exceptional magnetoelectric coupling phenomena and potential applications in next-generation spintronic devices. In this work, we successfully synthesized high-quality GdAlSi single crystals, a prototypical member of RAlX (R = rare earth elements; X = Si/Ge) family that has been theoretically predicted to sustain a non-trivial Weyl semimetal state. Through systematic investigations of magnetic and transport properties, we identified two successive antiferromagnetic transitions at critical temperatures TN1 31.9 K and TN2 31.1 K, as evidenced by temperature-dependent resistivity, magnetic susceptibility, and specific heat measurements. Notably, applied magnetic fields exceeding 8 T induce a third magnetic transition (TN3), generating a cascade of metamagnetic transitions that collectively form a dendritic phase diagram. This complex magnetic behavior is attributed to the interplay between localized Gd-4f moments and itinerant conduction electrons, possibly mediated by Dzyaloshinskii-Moriya interactions. Transport measurements revealed striking stepwise anomalies in magnetoresistance when crossing phase boundaries, accompanied by pronounced hysteresis loops arising from magnetic moment flopping processes. Our results not only establish GdAlSi as a rich platform for investigating correlated topological states, but also demonstrate its potential for engineering topological phase transitions through magnetic symmetry manipulation in Weyl semimetals.

Figures (6)

• Figure 1: (a) Unit cell of GdAlSi. (b) Powder XRD pattern measured at room temperature. (c) EDS spectrum of the as-grown single crystal (inset: photograph of the crystal).
• Figure 2: (a) Temperature dependence of $\rho_{xx}$. Inset is the enlargement of the $\rho_{xx}$ around 32 K. (b) Temperatures dependence of $\rho_{xx}$ at different fields. (c) Field dependence of the MR at different temperatures with the $B \parallel c$ configuration. (d) Field dependence of the original data $\rho_{xx}$ under various temperatures between 2 K and 32 K. Arrows mark the critical field positions ($B_1$-$B_4$) corresponding to phase transitions identified from magnetoresistance anomalies.
• Figure 3: (a) Temperature dependence of magnetic susceptibility $\chi_c$ and 1/$\chi_c$ for $B \parallel c$ measured in an applied field of 0.1 T. (b) Temperature-dependent magnetic susceptibility under different fields. (c) Isothermal magnetization curves measured under applied fields of B = -14 T to 14 T at temperatures 2 - 32 K. The inset displays corresponding curves at 2 - 300 K under B = ±5 T. (d) Field derivative of magnetization ($dM/dB$) versus magnetic field (B) measured at temperatures 2 - 32 K under applied fields up to B = ±14 T. Labels $B_1$ and $B_2$ (black/blue arrows) denote anomalies emerging during ascending/descending field sweeps, respectively.
• Figure 4: (a) Temperature dependence of the specific heat $C(T)$ under different fields. (b) Magnetic field dependence of Hall resistivity at various temperatures. (c) Hall resistivity ($\rho_{yx}$) and (d) magnetoresistivity ($\rho_{xx}$) for magnetic fields applied along the $c$-axis ($\theta = 0^\circ$) and in the $ab$-plane ($\theta = 90^\circ$).
• Figure 5: (a)(b)(c), (d)(e)(f) Enlarged plots of $\rho_{xx}$, $\rho_{yx}$, and $M$ around the critical field $B_1$ and $B_2$ of the metamagnetic transition at 24 K and 28 K, respectively. The blue arrows indicate the direction of the magnetic field sweep.