Probing magnetic anisotropy and spin-reorientation transition in 3D antiferromagnet single crystal Ho_0.5Dy_0.5FeO₃|Pt using spin Hall magnetoresistance

Rare-earth orthoferrites (REFeO₃), are 3D antiferromagnets (AFM) that exhibit a weak ferromagnetism originating from slight canting of the spin moments and display a variety of spin reorientation transitions in the magnetic field (H)-temperature (T) parameter space. We present spin Hall magnetoresistance (SMR) studies on a b-plate of single crystal Ho_0.5Dy_0.5FeO₃|Pt hybrid, carried out by rotating H in the ac-plane (α-scan) at various T down to 11 K. At 300 K (H ≥ 800 Oe) in Γ₄(G_x, A_y, F_z) phase, SMR vs. α yielded a highly skewed curve with a sharp change, accompanied by a rotational hysteresis around a-axis. Notably, α-scans (H < 800 Oe) on the pre-pinned domain (±F_z domain) exhibited an anomalous sinusoidal signal of periodicity 360°. Low-T SMR (H = 2.4 kOe) resulted in a weakening of the anisotropy possibly due to the T-evolution of Fe-RE exchange coupling. Besides, below 25 K the SMR modulation showed an abrupt change around c-axis, marking the presence of Γ₂(F_x, C_y, G_z) phase. We have employed a simple Hamiltonian and computed SMR, to examine the observed SMR modulations. Our SMR studies not only serve as an effective probe for magnetic anisotropy and spin reorientation but also, highlight the potential of Ho_0.5Dy_0.5FeO₃ for future AFM spintronic devices.