Magnetoresistance enhancement in epitaxial magnetite films grown on vicinal substrates

Abstract

The magnetoresistance ͑MR͒ behavior of epitaxial magnetite Fe 3 O 4 grown on low-vicinal ͑small miscut͒ and high-vicinal ͑large miscut͒ MgO substrates is compared. Magnetization measurements on Fe 3 O 4 films on high-vicinal substrates showed reduced magnetic moment as compared with the films grown on low-vicinal MgO, which correlates well with the expected reduction in magnetic moment due to step edge induced additional antiphase boundaries ͑APBs͒ with out-of-plane shift vectors. The MR is significantly higher ͑12.3% at 2 T͒ for a 45 nm Fe 3 O 4 film on high-vicinal substrate than that observed ͑7.2% at 2 T͒ for a film on low-vicinal substrate. A strong anisotropy in the MR is observed in correlation with the direction of atomic step edges. In addition to the increase in MR, the field dependency of the MR is also modified. The observed modification in the magnetotransport behavior of epitaxial Fe 3 O 4 films is attributed to an enhanced spin scattering arising due to the presence of atomic height steps that lead to the formation of a greater density of antiferromagnetically coupled APBs.

Anomalous anisotropic magnetoresistance in epitaxialFe3O4thin films on MgO(001)

“…11,12 Magneto-transport studies in epitaxial magnetite films are mostly focused on the influence of APBs, disorder and strain. In a recent study, 13 we have shown that if these nano-scale defects in Fe 3 O 4 films are manipulated in an ordered fashion one can attain a sizable magnetoresistance.…”

Magnetic and transport properties of epitaxial stepped Fe3O4(100) thin films

“…28,29 The presence of anti-phase boundary defects in Fe 3 O 4 contribute to its unusual magnetic and transport properties, such as the magnetization non-saturation even at very high field, 30,31 the super-paramagnetic behavior in Fe 3 O 4 films, 32,33 and a greater MR response across the AF-APBs. [34][35][36] On the other hand, in polycrystalline Fe 3 O 4 thin films, interesting properties such as magnetic-transport, 37 spin-injection, 38 and charge ordering 39,40 have also been investigated and discussed. Therefore, it is worth investigating the magnetic properties of stepped epitaxial Fe 3 O 4 films produced on large miscut angle vicinal MgO substrates, as a high density APBs is expected along the step edges.…”

Antiferromagnetic interlayer exchange coupling between Fe3O4 layers across a nonmagnetic MgO dielectric layer

“…Details of the growth conditions used for Fe 3 O 4 layers are given elsewhere. 12 The NiO ͑15 nm͒ epilayer was deposited at a substrate temperature of 600°C with an oxygen partial pressure 5 ϫ 10 −6 Torr. After the NiO growth, the sample was cooled to 250°C and a 10 nm film of Fe 3 O 4 was grown to serve as the bottom FM layer.…”