Manipulation of in-plane uniaxial anisotropy in Fe∕MgO(001) films by ion sputtering

Zhan, Qingfeng; Vandezande, Stijn; Haesendonck, C. Van; Temst, Kristiaan

doi:10.1063/1.2789396

Cited by 47 publications

(82 citation statements)

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“…Ion-induced surface ripples on ferromagnetic thin films were found to create a tunable pronounced magnetic texture [9][10][11][12][13][14]. So-called wave-ordered nanostructures generated by lowenergy nitrogen ion irradiation of Si were investigated as periodic nanomasks to dope the channel region of field-effect transistors [15].…”

Section: Introductionmentioning

confidence: 99%

Designing self-organized nanopatterns on Si by ion irradiation and metal co-deposition

2014

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Dot and ripple nanopatterns on Si surfaces with defined symmetry and characteristic dot spacings of 50-70 nm were created by 1 keV Ar ion irradiation at normal incidence and simultaneous co-deposition of Fe atoms at grazing incidence. Fe was continuously supplied from different sputter targets surrounding the Si substrate, leading to a steady-state Fe content in the near-surface region of the substrates. The pattern formation is self-organized, most probably caused by ion-induced phase separation. Patterns were analyzed with atomic force microscopy and the Fe content in the irradiated layer was measured with Rutherford backscattering. The symmetries of the produced patterns are isotropic, four-fold symmetric, three-fold symmetric and various types of two-fold symmetric patterns, depending on the geometrical arrangement of the sputter targets. Pattern formation was studied for a steady-state coverage of Fe between 0.5 and 3.3 × 10 15 Fe cm −2 . The threshold coverage for the onset of pattern formation is about 0.5-1 × 10 15 Fe cm −2 . The coherence length of the patterns is comparable to the average dot spacing. Nevertheless, the autocorrelation analysis reveals a residual long-range periodicity of some patterns. The dot spacing can be adjusted between about 20 nm and several hundred nm depending on the ion species and ion energy.

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Section: Introductionmentioning

confidence: 99%

Designing self-organized nanopatterns on Si by ion irradiation and metal co-deposition

2014

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“…4(c o ± 2δ DW nucleations [18]. The UMA component K u1 and the DW nucleation energies ǫ 90 o ±2δ can be evaluated by fitting the φ dependence of the experimental switching fields [8,17,18]. In Figs.…”

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confidence: 99%

Surface morphology and magnetic anisotropy of Fe/MgO(001) films deposited at oblique incidence

Zhan

Haesendonck

Vandezande

et al. 2009

Applied Physics Letters

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We have studied surface morphology and magnetic properties of Fe/MgO(001) films deposited at an angle varying between 0 o and 60 o with respect to the surface normal and with azimuth along the Fe [010] or the Fe[110] direction. Due to shadowing, elongated grains appear on the film surface for deposition at sufficiently large angle. X-ray reflectivity reveals that, depending on the azimuthal direction, films become either rougher or smoother for oblique deposition. For deposition along Fe[010] the pronounced uniaxial magnetic anisotropy (UMA) results in the occurrence of "reversed" two-step and of three-step hysteresis loops. For deposition along Fe[110] the growth-induced UMA is much weaker, causing a small rotation of the easy axes.Magnetic anisotropy of epitaxial films and its relationship to surface morphology have attracted much attention in recent years [1]. Both film properties are intimately related to the molecular beam epitaxy (MBE) deposition process. Oblique incidence deposition results via a self-shadowing effect [2,3] in the formation of grains in the plane of the film that are elongated perpendicular to the incident flux direction and with aspect ratio increasing at larger deposition angle with respect to the surface normal [4]. Consequently, an in-plane uniaxial magnetic anisotropy (UMA) with easy axis perpendicular to the incident flux direction is induced during growth of the magnetic films [4,5,6]. UMA was found to play an important role in determining the magnetization reversal in thin films of cubic systems [7,8]. Depending on the strength and orientation of the UMA, hysteresis curves with one, two and three steps are observed in various films at different field orientation. The appearance of the steps can be explained in terms of nucleation and propagation of domain walls (DWs) [8,9]. Consequently, understanding the influence of oblique incidence growth is very important because of its ability to control both magnetic anisotropy and surface morphology [10,11,12].Although shadowing effects have been studied in many magnetic systems, including Fe on MgO(001) [13] and Co on Cu(001) [14], the plane of oblique incidence was always kept parallel to the in-plane cubic easy axes of the magnetic layers. Here, we report on the influence of oblique deposition on the surface morphology and magnetic properties of Fe/MgO(001) films for deposition azimuth both along the Fe Fig. 1(c)). The elongated grains are believed to result from a redistribution of the incident flux due long-range attractive forces [15,16]. During evaporation the incident Fe atoms arrive preferentially on top of already formed grains rather than behind these grains. This shadowing effect is also observed for film deposition at 60 o with azimuth along [110]. The Fe grains on the surface are rhombic in shape with typical length of 15 nm and typical width of 6 nm (see Fig. 1(d)). Based on the STM images we conclude that the self-shadowing effect can be neglected for a deposition angle below 30 o . Moreover, the self-shadowing effect is...

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“…K 1 and K u are the magnetocrystalline anisotropy constant and the UMA constant, respectively. We rely on the two-jump domain wall motion model to explain the magnetization reversal in samples 1 and 2 [8,26]. φ u is fixed at 3π/4 according to the larger magnitude of the lower switching field (H c1 ) for ϕ = 3π/4 than for ϕ = π/4.…”

Section: B Magnetization Reversalmentioning

confidence: 99%

“…The angular dependence clearly reveals fourfold symmetry with the hard axis along the 100 directions and the easy axis along the 110 directions. Taking into account both the magnetocrystalline anisotropy and the UMA, the total free energy density is given by [8] …”

Section: B Magnetization Reversalmentioning

confidence: 99%

“…In particular, grazing-incidence ion beam sputtering has been demonstrated as a reliable tool to manipulate the magnetic anisotropy. The sputtering results in the development of nanoscale surface ripples, giving rise to an in-plane uniaxial magnetic anisotropy (UMA) with controllable orientation and strength through the sputtering conditions [5][6][7][8][9]. Bisio et al employed ion beam sputtering to achieve step-induced UMA in Fe films on flat Ag (001) substrates [10].…”

Section: Introductionmentioning

confidence: 99%

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Tailoring the magnetic anisotropy, magnetization reversal, and anisotropic magnetoresistance of Ni films by ion sputtering

et al. 2015

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We studied surface morphology induced changes of magnetic anisotropy, magnetization reversal, and symmetry of the anisotropic magnetoresistance (AMR) in ion sputtered Ni films grown on MgO (001). Grazing-incidence ion sputtering generally develops anisotropic surface roughness of the Ni films, i.e., nanometer wide ripples parallel to the ion beam direction, giving rise to uniaxial magnetic anisotropy with the easy axis along the ion beam direction. The formed ripples act as domain wall nucleation and pinning sites during magnetization reversal, while two-jump domain wall motion dominates in the as-grown Ni films. More importantly, the azimuthal angular dependence of the AMR indicates a superposition of twofold symmetry and fourfold symmetry. By relying on grazing-incidence ion sputtering along specific crystallographic directions, we are able to tailor the relative weight of twofold and fourfold symmetry of AMR. We demonstrate that in contrast to the bulk case, the symmetry of the AMR becomes also sensitive to the surface morphology in thin films, which is in particular relevant for the design of magnetotransport based sensors.

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Manipulation of in-plane uniaxial anisotropy in Fe∕MgO(001) films by ion sputtering

Cited by 47 publications

References 13 publications

Designing self-organized nanopatterns on Si by ion irradiation and metal co-deposition

Designing self-organized nanopatterns on Si by ion irradiation and metal co-deposition

Surface morphology and magnetic anisotropy of Fe/MgO(001) films deposited at oblique incidence

Tailoring the magnetic anisotropy, magnetization reversal, and anisotropic magnetoresistance of Ni films by ion sputtering

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