Magnetic Properties of Epitaxial Fe3O4 Films

Abstract

Epitaxial magnetite thin films with (100), (110) and (111) orientation have been deposited by Laser ablation onto substrates with [NaCl] and [Spinel] structure. X-ray difraction revealed pseudomorphic growth for (100) and (111) oriented films on MgO (100) and ZnFe2O4 (111) respectively, whereas films on MgAl2O4 showed a high degree of relaxation. For films on MgAl2O4 and ZnFe2O4 a significant enhancement of the Verwey-transition temperature compared to bulk material has been observed. The influence of stress on the magnetic anisotropy has been investigated by torque-magnetometry on (110) oriented films. Both films on MgO and spinel show an [110] in plane easy axis, which can be explained by (tensile) stresses in the case of MgO but not in the case of spinel. CEMS pattern indicate out of plane components of the magnetisation for all films. We suggest cation antiphase boundaries, observed by TEM to be responsible for this effect, limiting the magnetic coherence length and thus reducing shape anisotropy.