Probing magnetic anisotropy and spin-reorientation transition in 3D antiferromagnet, Ho$_{0.5}$Dy$_{0.5}$FeO$_{3}\vert$Pt using spin Hall magnetoresistance

Abstract

Orthoferrites (REFeO 3 ) containing rare-earth (RE) elements are 3D antiferromagnets (AFM) that exhibit characteristic weak ferromagnetism originating due to slight canting of the spin moments and display a rich 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 (acplane) of crystalline Ho 0.5 Dy 0.5 FeO 3 |Pt hybrid at various T in the range, 11 to 300 K. In the room temperature Γ4(Gx, Ay, Fz) phase, the switching between two degenerate domains, Γ4(+Gx, +Fz) and Γ4(−Gx, −Fz) occurs at fields above a critical value, Hc ≈ 713 Oe. Under H > Hc, the angular dependence of SMR (α-scan) in the Γ4(Gx, Ay, Fz) phase yielded a highly skewed curve with a sharp change (sign-reversal) along with a rotational hysteresis around a-axis. This hysteresis decreases with an increase in H. Notably, at H < Hc, the α-scan measurements on the single domain, Γ4(±Gx, ±Fz) exhibited an anomalous sinusoidal signal of periodicity 360 deg. Low-T SMR curves (H = 2.4 kOe), showed a systematic narrowing of the hysteresis (down to 150 K) and a gradual reduction in the skewness (150 to 52 K), suggesting weakening of the anisotropy possibly due to the T -evolution of Fe-RE exchange coupling. Below 25 K, the SMR modulation showed an abrupt change around the c-axis, marking the presence of Γ2(Fx, Cy, Gz) phase. We have employed a simple Hamiltonian and computed SMR to examine the observed skewed SMR modulation. In summary, SMR is found to be an effective tool to probe magnetic anisotropy as well as a spin reorientation in Ho 0.5 Dy 0.5 FeO 3 . Our spin-transport study highlights the potential of Ho 0.5 Dy 0.5 FeO 3 for future AFM spintronic devices.