Anisotropic in-plane magnetoresistance and Hall effect in Weyl metal SrRuO₃ thin films

Weyl semimetals (WSMs) are a unique class of topological materials, possessing Fermi-arc surface states and exhibiting the chiral anomaly effect. The chiral anomaly effect refers to a non-equilibrium charge transfer within a Weyl-node pair of opposite chirality under the condition of E // B, leading to non-conserved chiral charges and thus enhanced electrical conductivity. In experiments, such enhanced conductivity due to the chiral anomaly manifests as a negative longitudinal magnetoresistance (MR) when external B is applied along the bias current direction I.

In this work, we present rigorous φ-dependent and α-dependent magnetotransport measurements to investigate such negative longitudinal MR due to chiral anomaly in a sunbeam device fabricated from an untwinned Weyl metal SrRuO₃ (SRO) thin film. Here, φ and α represent angles from the bias current direction to the in-plane magnetic field direction and the SRO orthorhombic [001]_o, respectively. For φ = 0^o (E // B), we observed a large magnitude of negative longitudinal MR for the two Hall-bar devices oriented along [001]_o (α=0^o) and [1-10]_o (α=90^o), and it gives negligible longitudinal MR for α ~ 45^o. On the other hand, the in-plane Hall signal exhibits nearly φ-independent behavior for α = 0^o and 90^o devices. These results cannot be explained by conventional anisotropic MR and planar Hall effects in magnetic systems, and the chiral anomaly effect and tilted Weyl nodes in SRO may play important roles. Detailed band calculations with different magnetization orientations will also be presented and discussed to elucidate the observed anisotropic in-plane MR and Hall effect.