The predominance of substrate induced defects in magnetic properties of Sr₂FeMoO₆thin films

Abstract

A systematic study of epitaxially grown Sr2FeMoO6 thin films on SrTiO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, SrLaAlO4 and MgO single crystal substrates were made. Transmission electron microscopy investigations showed sharp substrate/films interfaces and increased defect concentration with increased lattice mismatch, indicating defect formation such as dislocations, low angle grain boundaries and stacking faults as a strain relaxation mechanism. Large enough compressive mismatch cause the over-relaxation of the lattice parameters through reorganization or interface defects, which was observed as a tensile strain in films with compressive mismatch larger than -1.05%. All the films with compressive mismatch were phase pure and epitaxially textured while signatures of SrMoO4 parasitic particle was found only in the film grown on MgO. No correlation between the antisite disorder and other structural defects or magnetic properties were found. Instead, the saturation magnetization, Curie temperature, magnetic domain rotation etc are higly dependent on the lattice mismatch induced defects, which outshines the possible correlation with B-site ordering.

Challenges in Sr2FeMoO6−δ Thin Film Deposition

“…[5]. The higher T C and reduced M s in tensile‐strained films suggest that tensile strain and interface defects promote the formation of oxygen vacancies . According to ref.…”

“…In particular, it appeared during postdeposition cooling in an oxygen atmosphere . SrMoO 4 formation is favored by biaxial tensile film strains . During pulse laser deposition of thin films at 820 °C, over 850 °C, at 900 °C, and at 950 °C, decomposition of SFMO into SrMoO 4 and other oxides was obtained already at p O2 > 10 −2 Pa.…”

“…Strain can be tuned by varying the substrate, using different buffer layers or by changing the thickness of the film . By tuning the level of strain from compressive to tensile with the use of different buffer layers, switching of magnetocrystalline anisotropy from an in‐plane to an out‐of‐plane state has been demonstrated in SFMO thin films …”

“…The higher T C and reduced M s in tensile-strained films suggest that tensile strain and interface defects promote the formation of oxygen vacancies. [110] According to ref. [5], the formation energies of in-plane (O xy ) and out-of-plane (O z ) vacancies decrease differently in dependence on both tensile and compressive biaxial strain.…”

Coherent Fe-rich nano-scale perovskite oxide phase in epitaxial Sr2FeMoO6 films grown on cubic and scandate substrates

“…This strain energy stored in the films grows as the film thickness increases and, when it becomes so large that relaxation becomes energetically favorable, it is released with the addition of dislocations or other structure defects in the film after a critical thickness value. 12,13 These defects impose serious limitations for technological applications since they will alter the transport/magnetic properties of SFMO films severely.…”