The magnetization of epitaxial nanometric CoFe2O4(001) layers

Abstract

We have studied the magnetic anisotropy of nanometric CoFe 2 O 4 ͑CFO͒ thin films grown on ͑100͒SrTiO 3 ͑STO͒ substrates. It has been found that epitaxial substrate-induced compressive strain makes the normal-to-film axis harder than the in-plane directions. In agreement with some previous reports, the magnetization loops are found to display a characteristic shrinking at low fields. Detailed structural and microstructural analyses, together with a modeling of the magnetization loops, revealed that the microstructure of the films, namely, the coexistence of a continuous CFO and a distribution of pyramidal CFO huts emerging from the surface, are responsible for this peculiar feature. We argue that this behavior, which significantly impacts the magnetic properties, could be a general trend of spinel films grow on ͑001͒STO substrates.

Spin Hall Magnetoresistance as a Probe for Surface Magnetization inPt/CoFe2O4Bilayers

“…Figure 5a shows the hysteresis loops M(H) of the Pt(2 nm)/CFO(40 nm) sample obtained by VSM when applying the magnetic field H along t and n directions at 50 K. As can be seen from the hysteresis loop when the field is applied in plane, M(H||t) curve, the large coercive fields  0 H c (t) ≈ ±1.2 T and the fact that hysteresis only disappears at ≈ 5 T are signatures of the strong magnetic anisotropy typical of CFO thin films [54,55]. The shape of the hysteresis loop when the field is applied out of plane, M(H||n), indicates a harder magnetization axis and, correspondingly, the coercive field  0 H c (n) ≈ ±0.44 T and the magnetic remanence are smaller.…”

“…Characteristic steps are observed in the hysteresis loops around zero field. These step-like features are commonly found in CFO thin films [54,60] and other ferrimagnetic oxides such as Fe 3 O 4 [57] or -Fe 2 O 3 [61], and have been attributed to the result of coupled antiferromagnetic domains due to the presence of APBs by Sofin et al [62]. A larger density of APBs would lead to a larger step at zero field.…”

Controlling the electronic structure of Co1−xFe2+xOMoyer1, Vaz2, Negusse3 et al. 2011Phys. Rev. B8917740View full textAdd to dashboardCite

“…17,46 Thin films (~ 40 -120 nm) grown on high symmetry substrates, such as MgO and SrTiO 3 , show a reduced saturation magnetization of 25 -60% of bulk values. 43,[46][47][48] The reduction of saturation magnetization in other ferrites has been attributed to anti-phase boundaries, 49 which are created when crystal growth begins at different locations on the substrate, forming islands that are structurally out of phase with each other upon merging, giving rise to spin frustration at the boundaries. For ultrathin films (< 7 nm), the saturation magnetization of cobalt ferrite increases above the bulk value due to increased mixing of the cations between the octahedral and tetrahedral sites.…”

“…For ultrathin films (< 7 nm), the saturation magnetization of cobalt ferrite increases above the bulk value due to increased mixing of the cations between the octahedral and tetrahedral sites. 47 It has a large magnetic critical temperature (T c = 793 K) and is more environmentally stable than magnetite since Co 2+ and Fe 3+ are the most stable valence states of those cations, whereas Fe 2+ cations easily oxidize to Fe 3+ . 50 When cobalt ferrite is doped with extra iron, Co 1-x Fe 2+x O 4 , Fe 2+ cations are expected to substitute for the Co 2+ cations.…”

Topographic anisotropy in continuous magnetic films with two-dimensional surface nanomodulation

“…10 Recently, recording and magnetoelectric applications have attracted a great deal of renewed interest in how surface variation/roughening will affect the properties of magnetic films. [11][12][13][14][15][16] To verify the extensive theoretical works, experiments on magnetic films with well defined, quantified, and specifically designed structures are required. In this manuscript, we present the results of a detailed study into the magnetic behavior of a soft magnetic Ni 45 Fe 55 alloy film with a circular nanodent array as surface modulation.…”