Impact of growth conditions on magnetic anisotropy and magnon Hanle effect in α-Fe₂O₃

The antiferromagnetic insulator α-Fe₂O₃ (hematite), commonly used in spintronics and magnonics, undergoes a spin-reorientation transition (Morin transition) at around 263 K. This Morin transition is often absent in thin films, limiting their potential for applications. To tune the Morin transition temperature, we explore different growth conditions and their impact on the magnetic anisotropy of α-Fe₂O₃ films. We compare the structural, magnetic, and magnon-based spin transport properties of α-Fe₂O₃ films with different thicknesses grown via pulsed laser deposition in molecular and additional atomic oxygen atmospheres. Notably, α-Fe₂O₃ films grown with additional atomic oxygen exhibit a finite Morin transition even down to thicknesses of 19 nm. Furthermore, we observe a clear impact of the growth conditions on the magnon Hanle effect, i.e., the precession of magnon pseudospin around its equilibrium pseudofield in easy-plane antiferromagnets. In all-electrical magnon transport measurements, we detect distinct changes in the magnon spin signal for α-Fe₂O₃ films grown with atomic oxygen, including an enhanced maximum of the magnon Hanle signal and a shift of the magnon Hanle peak to lower magnetic field values. This suggests altered magnetic anisotropy due to an increased oxygen content, offering insights for tuning the magnetic properties of α-Fe₂O₃ films [1].

[1] M. Scheufele et al., APL Mater. 11, 091115 (2023).