We describe an arrangement in which the magnetization components parallel and perpendicular to the applied field are both determined from longitudinal magneto-optic Kerr effect measurements. This arrangement differs from the usual procedures in that the same optical geometry is used but the magnet geometry altered. This leads to two magneto-optic signals which are directly comparable in magnitude thereby giving the in-plane magnetization vector directly. We show that it is of great value to study both in-plane magnetization vector components when studying coupled structures where significant anisotropies are also present. We discuss simulations which show that it is possible to accurately determine the coupling strength in such structures by examining the behavior of the component of magnetization perpendicular to the applied field in the vicinity of the hard in-plane anisotropy axis. We illustrate this technique by examining the magnetization and magnetic anisotropy behavior of ultrathin 0 0Co/Cu(111)/Co (dc"=20A and 27 A) trilayer structures prepared by molecular beam epitaxy, in which coherent rotation of the magnetization vector is observed when the magnetic field B is applied along the hard in-plane anisotropy axis, with the magnitude of the magnetization vector constant and close to its bulk value. Results of micromagnetic calculations closely reproduce the observed parallel and perpendicular magnetization loops, and yield strong uniaxial magnetic anisotropies in both layers, while the interlayer coupling appears to be absent or negligible in comparison with the anisotropy strengths.
Epitaxial Co has been grown on GaAs(001) and studied by both low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED), and by the magneto-optic Kerr effect (MOKE) and polarized neutron reflection (PNR). Three samples were fabricated using different growth procedures: (1) ‘‘interrupted’’ growth (including an anneal); (2) and (3) continuous growth of similar thicknesses. For sample 1, RHEED patterns indicate an initial growth in the bcc phase followed by a relaxation into a distorted single phase at completion of growth, whereas samples 2 and 3 showed a multicrystalline structure after growth. LEED patterns were used to check the existence of the 2×4 reconstruction patterns before growth, but no LEED patterns could be obtained after more than 2 Å Co was deposited, in contrast to the RHEED patterns which remained visible throughout the growth. Structural analysis of the completed films indicates the formation of a ∼10 Å CoO layer on the Co/air interface, and gives thicknesses for magnetic material of (1) 30 Å and (2) 80 Å. Sample 1 showed a dominant fourfold magnetic anisotropy with the easy axis parallel to the (100) direction and with a strength 2K4/M of ∼0.5 kOe, smaller in magnitude than that reported for bcc films on GaAs(110) but along the same axis [G. A. Prinz et al., J. Appl. Phys. 57, 3672 (1985)]. However, samples 2 and 3 showed only a large uniaxial anisotropy along the (110) direction of strength 2K1/M of ∼1.5 kOe and ∼2.5 kOe, respectively, similar in magnitude to those previously observed [G. A. Prinz et al., J. Appl. Phys. 57, 3676 (1985)]. We attribute the origin of the contrasting magnetic anisotropy behavior observed to the differences in final structure.
In situ control of electronic phase separation in La1/8 Pr4/8Ca3/8MnO3/PNM-PT thin films using ferroelectricpoling-induced strain J. Appl. Phys. 113, 013705 (2013) Transport and magnetic properties of Fe doped CaMnO3 J. Appl. Phys. 112, 123913 (2012) Simulations of magnetic nanoparticle Brownian motion J. Appl. Phys. 112, 124311 (2012) Ferromagnetism, hysteresis and enhanced heat dissipation in assemblies of superparamagnetic nanoparticles J. Appl. Phys. 112, 114912 (2012) Defect mediated reversible ferromagnetism in Co and Mn doped zinc oxide epitaxial films J. Appl. Phys. 112, 113917 (2012) Additional information on J. Appl. Phys. In this article we present the results of a detailed study of the switching behavior observed in epitaxial single Fe films of thickne.ss between 30 and 450 A, and a wedge shaped Fe film with a thickness range of 111-60 ,& grown on GaAs (001). These films have cubic and uniaxial anisotropies which change with film thickness. For the fixed thickness films the values of the anisotropy constants were accurately determined by Brillouin light scattering (BLS) measurements together with polar magneto-optic Kerr effect (MOKE) measurements that gave the value of the magnetization. The switching behavior of these samples was observed with in-plane MOKE magnetometry as a function of the angle between the applied field and the in-plane crystallographic axes. Measurements of the component of magnetization perpendicular to the applied field allow a precise determination of the relative orientation of the hard and easy in-plane anisotropy axes. This can be used to accurately determine the ratio of uniaxial to cubic anisotropy constants, when this ratio is less than one. The ratios obtained from MOKE agree well with those obtained from BLS. Minimum energy calculations predict that the reversal process should proceed by a continuous rotation of the magnetization vector with either one or two irreversible jumps, depending on the applied field orientation and the nature of the anisotropy of the film. The calculations provide a good qualitative description of the observed reversal process, although the magnetic microstructure influences the exact values of the switching fields.
Polar Kerr measurements have been used to measure the dependence of the biquadratic coupling strength B 12 on Cr thickness in an Fe/Cr/Fe trilayer. The overall behavior, which consists of a maximum coupling strength at d Cr ϭ5 Å ͑3.5 ML͒ with a falloff at greater Cr thicknesses, is found to be consistent with in-plane Kerr and Brillouin light-scattering measurements performed on the same sample. The polar Kerr measurements suggest additionally that B 12 increases from zero near zero Cr thickness, and that it oscillates in magnitude after the first peak, with a second peak in B 12 occurring at about d Cr ϭ12 Å ͑8.3 ML͒. The positions and heights of the first and second biquadratic coupling maxima, in relation to the first bilinear coupling maximum, show excellent agreement with previous measurements by Köbler et al. of the biquadratic coupling behavior in Fe/Cr/Fe, and also show good agreement with the predictions of an intrinsic biquadratic coupling mechanism due to Edwards et al. ͓S0163-1829͑97͒09117-0͔
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