Structure, magnetic ordering, and spin filtering efficiency of NiFe2O4(111) ultrathin films

S. Matzen (1) , J.-B. Moussy (1) , P. Wei (2) , Christophe Gatel (3) , J. C. Cezar (4) , M. A. Arrio (5) , Ph. Sainctavit (5) , J. S. Moodera (2)

1 SPCSI - Service de Physique et de Chimie des Surfaces et Interfaces
2 Francis Bitter Magnet Laboratory
3 CEMES - Centre d'élaboration de matériaux et d'études structurales
4 ESRF - European Synchrotron Radiation Facility
5 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie

NiFe2O4(111) ultrathin films (3-5 nm) have been grown by oxygen-assisted molecular beam epitaxy and integrated as effective spin-filter barriers. Structural and magnetic characterizations have been performed in order to investigate the presence of defects that could limit the spin filtering efficiency. These analyses have revealed the full strain relaxation of the layers with a cationic order in agreement with the inverse spinel structure but also the presence of antiphase boundaries. A spin-polarization up to þ25% has been directly measured by the Meservey-Tedrow technique in Pt(111)/NiFe2O4(111)/c-Al2O3(111)/Al tunnel junctions. The unexpected positive sign and relatively small value of the spin-polarization are discussed, in comparison with predictions and previous indirect tunnelling magnetoresistance measurements

Domaines: Physique Quantique [quant-ph]; Science des matériaux [cond-mat.mtrl-sci]

S. Matzen, J.-B. Moussy, P. Wei, Christophe Gatel, J. C. Cezar, et al.. Structure, magnetic ordering, and spin filtering efficiency of NiFe2O4(111) ultrathin films. Applied Physics Letters, 2014, 104 (18), pp.182404. ⟨10.1063/1.4871733⟩. ⟨hal-01021365⟩