F. Stobiecki

MOSSBAUER STUDY OF ION-BEAM MIXING OF FE/ZR MULTILAYERS

The Ar‐ion‐beam mixing of Fe/Zr multilayers is studied in detail by conversion electron Mossbauer spectroscopy (CEMS) and x‐ray diffraction (XRD). The dependence of the ion‐beam induced amorphization and interfacial mixing on the sublayer thickness and ion dose (1×1013–2×1016 Ar/cm2) is studied systematically for samples with Fe to Zr thickness ratios dFe/dZr=1 and 0.5 and modulation wavelengths Λ=dFe+dZr of 5–80 nm and 7.5–90 nm, respectively. The CEMS results allowed the evaluation of the mixing efficiency from the thickness of the mixed layers. The experimentally determined mixing efficiency was compared with theoretical estimates based on the ballistic collision and thermal spike models, showing good agreement with the predictions of the modified ballistic collision model. For high degrees of amorphization the composition of the amorphous phase formed due to ion‐beam mixing is close to the nominal composition of the sample, as revealed by CEMS measurements. These results were compared with those obtai...

Co/Au multilayers with graded magnetic anisotropy for magnetic field sensing

A concept of a magnetoresistive sensor for magnetic fields based on a Au/Co-wedge/Au/Co/Au multilayer is proposed. The wedged Co layer is characterized by a laterally changing coercivity resulting from a gradient of perpendicular magnetic anisotropy. Its magnetization reversal in a perpendicular magnetic field takes place by movement of a single domain wall in the direction parallel to the anisotropy gradient. The magnetization reversal of the multilayer has been investigated by magnetooptical and magnetoresistive measurements. The resistance of the proposed film system correlates well with the position of the domain wall and thus it can be used to sense magnetic fields.

Antiferromagnetic magnetostatic coupling in Co/Au/Co films with perpendicular anisotropy

Magnetization reversal processes in Au/Co/Au-wedge/Co/Au pseudo-spin-valve structures characterized by perpendicular anisotropy of 0.6-nm-thick Co layers were investigated by magneto-optical Kerr effect. The samples were deposited on a Ti/Au buffer layer of differing Au-layer thickness (different surface roughness and crystallite size). The distinctive influence of the buffer layer thickness on the dependences of switching fields, and energy of the effective interlayer coupling, versus Au spacer thickness is presented. In particular, increasing the buffer-layer thickness results in a decrease in the oscillation amplitude of the Ruderman–Kittel–Kasuya–Yosida-type interaction and in the enhancement of the antiferromagnetic coupling related to magnetostatic (orange peel) interactions.

Creation of Out-of-Plane Magnetization Ordering by Increasing the Repetitions Number

The influence of the Co layer thickness as well as the number of repetitions N on the magnetic properties of (Co/Au)N multilayers was investigated systematically using magneto-optical techniques, vibrating sample magnetometry, and magnetic force microscopy. The studies focused on the characteristics of magnetic hysteresis loops in connection with magnetic domain structure parameters. Increasing the repetitions number, an out-of-plane magnetization ordering is created for Co layers with a thickness larger than the single-layer thickness at which the spin reorientation transition occurs.

N

Material selective sensitivity of a magneto-optical polar Kerr effect to magnetizations of films from different materials in a multilayer system is presented. The method is supported by rigorous modeling of magneto-optic response from the multilayer system and by experimental demonstration on the periodic cobalt-permalloy multilayers [Ni80Fe20(2 nm)/Au(2 nm)/Co(0.4, 0.8, and 1.2 nm)/Au(2 nm)]10 .

in (Co/Au)

Graded anisotropy magnetic materials possess a coercive field changing laterally with position. A simple fabrication procedure to produce such an anisotropy gradient in a polycrystalline Au/Co layer system without lateral thickness variation and with perpendicular magnetic anisotropy, prototypical for a large variety of thin film systems, is shown. The procedure uses light-ion bombardment without the use of a mask. Magnetization reversal in this polycrystalline layer system takes place by unidirectional movement of a single domain wall only in regions with larger anisotropies and anisotropy gradients. In this anisotropy/anisotropy gradient regime, the domain wall is oriented perpendicular to the coercive field gradient, and it can be positioned along the gradient by an appropriate magnetic field pulse. For smaller anisotropies/anisotropy gradients, the natural anisotropy fluctuations of the polycrystalline layer system induce magnetization reversal dominated by domain nucleation.PACS75.30.Gw; 75.70.Cn; 75.60.Ch

_{\rm N}

The perpendicular exchange bias in NiO(antiferromagnet)/Co(ferromagnet) polycrystalline layer films is studied. It is found that the NiO layer forces the Co layer magnetization to be oriented perpendicular to the film plane in a greater thickness range than is found in the Au/Co/Au system. Simultaneously, a large coercivity and a significant perpendicular exchange bias field were observed that are owing to the interlayer exchange bias coupling between NiO and Co, which supports the perpendicular magnetic anisotropy of the Co layer. These findings are confirmed by magnetometry and magnetoresistance measurements.