Magnetic anisotropies of sputtered Fe films on MgO substrates

Goryunov, Yu. V.; Garif’yanov, N. N.; Khaliullin, Giniyat; Гарифуллин, И. А.; Тагиров, Л. Р.; Schreiber, Frank; Mühge, Th.; Zabel, H.

doi:10.1103/physrevb.52.13450

Cited by 98 publications

(53 citation statements)

References 22 publications

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“…In particular, the value 2K 1 /M ϭ0.30 kOe obtained for the uncovered Fe͑60 Å͒ layer is very close to the value 0.34 kOe measured for Fe͑50 Å͒/Si͑111͒. 10 The observed linewidth for the Fe͑60 Å͒ film was approximately 37 Oe, close to the best values observed for Fe and other transition metal films, 14,15 indicating the good crystallinity of the samples. Figure 2 shows the variation of the linewidth versus in-plane angle for Nd͑10 Å͒/Fe͑100 Å͒/ Si͑111͒.…”

Section: A Resonance Field and Linewidthsupporting

confidence: 64%

Magnetic properties of Nd/Fe double layers grown on Si(111) by electron beam evaporation

Fermín

Azevedo

Rezende

et al. 1998

Journal of Applied Physics

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In-plane ferromagnetic resonance ͑FMR͒ has been used to study the room-temperature magnetic and crystalline properties of Nd/Fe bilayers. Several samples were grown by electron beam evaporation onto Si͑111͒ substrates, for various Fe and Nd thicknesses. The symmetry of the resonance field as a function of the azimuthal angle departs from the sixfold one expected for a ͑111͒Fe film. The FMR data were analyzed in the framework of a phenomenological model, which takes into account firstand second-order magnetocrystalline, uniaxial and perpendicular anisotropies. Our analysis reveals that the deviation from the sixfold symmetry is due to a combined effect of an induced uniaxial in-plane anisotropy with a small misorientation of the substrate surface from the ͑111͒ plane. We suggest that the in-plane uniaxial anisotropy may originate from an arrangement of ͑111͒ terraces separated by well oriented atomic steps formed during the small miscut. The effect of the Nd overlayer is to induce a perpendicular anisotropy which is not sufficiently large to overcome the demagnetizing field and push the magnetization entirely out-of-plane.

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Section: A Resonance Field and Linewidthsupporting

confidence: 64%

Magnetic properties of Nd/Fe double layers grown on Si(111) by electron beam evaporation

Fermín

Azevedo

Rezende

et al. 1998

Journal of Applied Physics

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“…In addition to this magnetocrystalline anisotropy, different structural and morphological factors can be sources of additional contributions to the effective anisotropy experimentally obtained in epitaxial Fe/ MgO͑001͒ films. For example, Goryunov et al 12 have reported an important surface anisotropy for film thicknesses around 1000 Å, which they attribute to strain relaxation extended as far as 45 Å from the film-substrate interface. Other reported sources of additional contributions to the magnetic anisotropy, usually of uniaxial character, are both deposition geometry, particularly for the oblique-incidence of Fe on MgO(001), [13][14][15] and the presence of steps in the substrate.…”

Section: Introductionmentioning

confidence: 99%

Coverage effects on the magnetism ofFe∕MgO(001)ultrathin films

Boubeta¹,

Clavero²,

García-Martín³

et al. 2005

Phys. Rev. B

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Different aspects of the structure-magnetism and morphology-magnetism correlation in the ultrathin limit are studied in epitaxial Fe films grown on MgO(001). In the initial stages of growth the presence of substrate steps, intrinsically higher than an Fe atomic layer, prevent the connection between Fe islands and hence the formation of large volume magnetic regions. This is proposed as an explanation to the superparamagnetic nature of ultrathin Fe films grown on MgO in addition to the usually considered islanded, or Vollmer-Weber, growth. Using this model, we explain the observed transition from superparamagnetism to ferromagnetism for Fe coverages above 3 monolayers (ML). However, even though ferromagnetism and magnetocrystalline anisotropy are observed for 4 ML, complete coverage of the MgO substrate by the Fe ultrathin films only occurs around 6 ML as determined by polar Kerr spectra and simulations that consider different coverage situations. In annealed 3.5 ML Fe films, shape or configurational anisotropy dominates the intrinsic magnetocrystalline anisotropy, due to an annealing induced continuous to islanded morphological transition. A small interface anisotropy in thicker films is observed, probably due to dislocations observed at the Fe/ MgO͑001͒ interface.

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“…[19] due to Co 70 Fe 30 having an arbitrary crystalline orientation. First, the equilibrium angle of free-layer magnetization (φ) under H ext with φ H is given by Eq.…”

mentioning

confidence: 99%

Spin-Torque Diode Measurements of MgO-Based Magnetic Tunnel Junctions with Asymmetric Electrodes

Matsumoto

Chanthbouala

Grollier

et al. 2011

Appl. Phys. Express

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We present a detailed study of the spin-torque diode effect in CoFeB/MgO/CoFe/NiFe magnetic tunnel junctions. From the evolution of the resonance frequency with magnetic field at different angles, we clearly identify the free-layer mode and find an excellent agreement with simulations by taking into account several terms for magnetic anisotropy. Moreover, we demonstrate the large contribution of the out-of-plane torque in our junctions with asymmetric electrodes compared to the in-plane torque. Consequently, we provide a way to enhance the sensitivity of these devices for the detection of microwave frequency.Spin-transfer torque (STT) in MgO-based magnetic tunnel junctions (MTJs) [1,2] is under development for device applications such as STT random access memories (STT-RAM) [3,4], domain-wall-motion MRAM, [5] racetrack memory [6] and spintronic memristors. [7,8] Recently, spin-torque diodes [9] have attracted much attention because their sensitivity for the detection of microwave frequency may exceed that of semiconductor diodes. [10,11] In the spin diode effect, an applied rf current to the MTJ exerts an oscillating spin torque on the magnetization of the free layer, leading to excitation of the ferromagnetic resonance (FMR) mode. The dynamics of the free layer cause oscillations of the tunnel magnetoresistance (TMR). As a result, the oscillating resistance partially rectifies the rf current and dc voltage is obtained (V diode ). The spin diode effect depends on the relative amplitudes (a J and b J ) of the classical inplane torque (T IP ) and the out-of-plane field-like torque (T OOP ). [12,13] Here, the torques are expressed as T IP = -γ(a J /M s )m×(m×M ref ) and T OOP = -γb J m×M ref with m (M s ) being the magnetization vector (the saturation magnetization) of the free layer, M ref the magnetization vector of the reference layer, and γ the gyromagnetic ratio. In spin diode spectra (V diode as a function of frequency (f )), the contribution of T IP (resp. T OOP ) results in a peak with a Lorentzian component (resp. an anti-Lorentzian component);where A and B are the amplitudes of the anti-Lorentzian component and Lorentzian component, f 1 is the resonance frequency, ∆ is the peak linewidth, H d is the outof-plane demagnetization field, and θ is the relative angle between the free layer and the reference layer. Experimentally evaluated T OOP was reported to reach over 25% of T IP in conventional CoFeB/MgO/CoFeB MTJs with symmetric electrodes. [12,13] However, in these MTJs, the dc bias dependence of T OOP is quadratic and symmetric with respect to the polarity of bias, leading to A = 0 at zero dc bias voltage. For MTJs with asymmetric electrodes, on the other hand, the bias dependence of T OOP is expected to be asymmetric and linear at low bias, [15,16] leading to larger A at zero dc bias voltage. In this study, we perform spin diode measurements of MgO-based MTJs with asymmetric electrodes. We also measure its dependence on magnitude and angle of the in-plane external magnetic field (H ext ) to identify the...

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Magnetic anisotropies of sputtered Fe films on MgO substrates

Cited by 98 publications

References 22 publications

Magnetic properties of Nd/Fe double layers grown on Si(111) by electron beam evaporation

Magnetic properties of Nd/Fe double layers grown on Si(111) by electron beam evaporation

Coverage effects on the magnetism ofFe∕MgO(001)ultrathin films

Spin-Torque Diode Measurements of MgO-Based Magnetic Tunnel Junctions with Asymmetric Electrodes

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