Control of spin-reorientation transition in (0001) oriented α-Fe₂O₃ thin film by external magnetic field and temperature

A pure-phase, unstrained and epitaxial α-Fe₂O₃ film of thickness 250 nm has been fabricated by reactive rf sputtering over c-Al₂O₃ substrate with nominal average surface roughness of 0.71 nm. Field induced spin-reorientation temperature (T_SR) and temperature dependent spin-reorientation field (H_SR) have been investigated. A linear relationship in the result has been found with ∂T_SR/∂H_SR equal to −0.92 ± 0.05 K kOe⁻¹ and −0.89 ± 0.175 K kOe⁻¹ by both methods, respectively. The field induced entropy change is argued to be the possible cause for the shift in the spin-reorientation temperature with applied field. The entropy change associated with the first-order phase transition is calculated on the basis of Clausius–Clapeyron equation and found to be 0.029 J kg⁻¹K⁻¹.