Unraveling the magnetic and electronic complexity of intermetallic ErPd ₂ Si ₂ : anisotropic thermal expansion, phase transitions, and twofold magnetotransport behaviour

Abstract We present a comprehensive investigation into the physical properties of intermetallic ErPd 2 Si 2 , a compound renowned for its intriguing magnetic and electronic characteristics. We confirm the tetragonal crystal structure of ErPd 2 Si 2 within the I 4/ mmm space group. Notably, we observed anisotropic thermal expansion, with the lattice constant a expanding and c contracting between 15 and 300 K. This behaviour is attributed to lattice vibrations and electronic contributions. Heat capacity measurements revealed three distinct temperature regimes: T 1 ~ 3.0 K, T N ~ 4.20 K, and T 2 ~ 15.31 K. These correspond to the disappearance of spin‐density waves, the onset of an incommensurate antiferromagnetic (AFM) structure, and the crystal‐field splitting and/or the presence of short‐range spin fluctuations, respectively. Remarkably, the AFM phase transition anomaly was observed exclusively in low‐field magnetization data (120 Oe) at T N . A high magnetic field ( B = 3 T) effectively suppressed this anomaly, likely due to spin‐flop and spin‐flip transitions. Furthermore, the extracted effective paramagnetic (PM) moments closely matched the expected theoretical value, suggesting a dominant magnetic contribution from localized 4f spins of Er. Additionally, significant differences in resistance ( R ) values at low temperatures under applied B indicated a magnetoresistance (MR) effect with a minimum value of −4.36%. Notably, the measured MR effect exhibited anisotropic behavior, where changes in the strength or direction of the applied B induced variations in the MR effect. A twofold symmetry of R was discerned at 3 and 9 T, originating from the orientation of spin moments relative to the applied B . Intriguingly, above T N , short‐range spin fluctuations also displayed a preferred orientation along the c ‐axis due to single‐ion anisotropy. Moreover, the R demonstrated a clear B dependence below 30 K. The magnetic‐field point where R transitions from linear B dependence to a stable state increased with temperature: ~ 3 T (at 2 K), ~ 4.5 T (at 4 K), and ~ 6 T (at 10 K). Our study sheds light on the magnetic and electronic properties of ErPd 2 Si 2 , offering valuable insights for potential applications in spintronics and quantum technologies.