Field and temperature dependence of Bloch walls across the thickness in Gd 0.28 Co 0.72 /Gd 0.12 Co 0.88 exchange coupled double layers (original) (raw)
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Journal of Magnetism and Magnetic Materials, 1990
Remagnetization of a 180 ° Bloch wall separating domains magnetized in the plane of a (100) LPE garnet thin film has been observed magnetooptically. (i) The process of saturation-to-saturation wall magnetization switch-overs has been studied and discussed. (ii) The coercive field of a Bloch line has been measured and found to be almost two orders of magnitude larger (10-20 Oe) than the coercive field of the Bloch wall (0.20e). (iii) Anhysteretic measurements have been carried out and the wall magnetization initial susceptibility found to be a quadratic function of the wall length.
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We have studied the interlayer coupling between Co and Gd-Co layers separated by nonmagnetic spacers in a series of [Co/X/ (Gd-Co)/X] 4 /Co multilayers (X ¼ Cu, Ti and Si). The exchange interaction at the interfaces causes 'macroscopic ferrimagnetic behavior' in the whole structure. The critical field for a spin-orientation transition H * leading to a non-collinear magnetic structure in multilayers gives an estimate of the coupling strength. The critical field decreases with the spacer thickness for all spacer materials. The temperature dependence of the critical field, however, depends strongly on the spacer material. The differences are attributed to the fact that, in contrast to Cu and Ti, using Si can reduce the Co magnetic moment. r
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The in-plane dynamics of ferrimagnetic Co/Gd multilayers are investigated by means of ferromagnetic resonance, magneto-optical Kerr effect and SQUID magnetometry. The power absorbed from these multilayers is strongly temperature dependent. For example, the resonant peak for a (Co 40 A /Gd 40 A)8 multilayer vanishes approximately 50 K below room temperature. We have further investigated Gd/Co/Gd and Tb/Co/Tb trilayers with different thicknesses of Gd (5-7 A), Tb (1-7 A) and Co (30-40 A). At room temperature, these Co-based trilayers show a shift of approximately 600 Oe at 24 GHz in the uniform ferromagnetic resonance field, compared to pure Co film, indicating the exchange coupling between the Co and Gd. The shift in the field for the resonance increases as the temperature is decreased. Furthermore the resonance linewidth increases as the temperature is decreased. The experimental results are in good agreement with our theoretical calculations.
Journal of Magnetism and Magnetic Materials, 2000
The micromagnetic structure and energy of a Bloch line (BL) in an asymmetric 1803 Bloch domain wall in a 60 nm +1 0 0, iron "lm have been calculated. In the wall cross-sections on either side of the BL, the #ux of magnetisation transverse to that of the domains was &C' shaped, roughly normal to the plane of the "lm in its interior but bending nearly parallel to the surfaces as they are approached. The sense of this transverse #ux is reversed at the BL. The energy of this BL was calculated to be considerably lower than the energies reported earlier for BLs in walls having &S' shaped transverse #ux cross-sections.
Physical Review B, 2006
We have grown ultrathin epitaxial Co films on three low-index surfaces of Pd. Their magnetic properties studied by the magneto-optical Kerr effect are correlated with the surface morphology analyzed by scanning tunneling microscopy. A perpendicular magnetic anisotropy in the films appeared after exposure to residual gas atmosphere at low temperature, after coverage with an Au overlayer or after annealing at 370 K and above. For one-and two-monolayer-thick films the hysteresis loops are reversed with respect to those of thicker Co films. This is due the negative polar Kerr rotation contribution from the Co/ Pd interface dominating over the positive polar Kerr rotation contribution from the noninterface part of the Co film. Reversed loops are not seen when the Co films grow in a three-dimensional mode. This indicates a clear correspondence between the mode of growth and the magneto-optical response. Near the film thickness where the Kerr rotation changes sign a remarkable temperature behavior is observed which is discussed as a superposition of two different magnetooptical contributions. The results qualitatively agree with the available ab initio band-structure calculations for the Co/ Pd multilayer structures with variable thickness of the Co layers.
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Applied Surface Science, 2007
A method for characterization of sub-nanometer thick Co/V and Co/Mo interfaces is proposed that uses magneto-optical ellipsometry. Both the polar Kerr rotation and ellipticity are fitted simultaneously to different models of interface layer. The magneto-optical data are measured for varying thicknesses of the cobalt layer and overlayer by scanning of a laser beam over the samples with two orthogonal wedges. Decrease of magneto-optical effect at both interfaces Co/Vand Co/Mo were observed, which corresponds to interface layers of thicknesses ranging from one to two monoatomic layers. In the case of vanadium, the interface layer is sharper and can be explained either by reduced magnetic moment of cobalt, or by anti-parallel magnetic moment of vanadium near the Co/V interface. #