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Magnetic transmission x-ray microscopy is a novel technique to image element specifically magnetic domain structures. A lateral resolution down to 25 nm is provided by the Fresnel zone plates used as optical elements in soft x-ray microscopy. The magnetic contrast is given by x-ray magnetic circular dichroism, i.e., large magnetic contributions up to 25% to the absorption cross section of circularly polarized x rays that occur in the vicinity of, e.g., the Fe L[sub 3,2] edges (706 and 719 eV) and depend on the relative orientation of the projection of the magnetization of the sample onto the photon propagation direction. Thus, both in-plane and out-of-plane contributions to the magnetization are accessible. Here we present images of the magnetic domain structure of a (3 nm Cr/50 nm Fe/6 nm Cr) thin film system with a preferentially in-plane magnetization recorded at the Fe L edges. The samples have been prepared by thermal evaporation onto a 100 nm thin Si[sub 3]N[sub 4! ] membrane and were mounted under a tilt of 30° with respect to the transmission direction of the photons in the full-field microscope. Corresponding images taken under a tilt of 0° ruled out out-of-plane contributions. Images recorded in applied varying external magnetic fields allowed to study the switching behavior. These trial results have a large impact on further investigations of nanostructured magnetic systems, e.g., spintronic devices and magnetic sensors with magnetic soft x-ray microscopy. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetization reversal of an array of 1 μm squared FeGd dots has been studied by magnetic transmission x-ray microscopy (MTXM). A (4 Å Fe/4Å Gd)x75 multilayered FeGd system has been prepared on a 30 nm thin Si[sub 3]N[sub 4] membrane by sputtering and structured by optical lithography and ion beam etching techniques. Both the domain structure within each single dot and the collective switching behavior could be observed with MTXM. A large variation in the nucleation field of the dots was found and can be attributed to the shape of the dots. A correlation between the nucleation field and the perimeter of each dot could be deduced. Hysteresis loops of individual dots are derived, taking into account the proportionality of the dichroic contrast to the magnetization of the sample. The stepped profile of the magnetization loop of a single dot is found to be clearly distinct from a continuous film. The high lateral resolution and the possibility to record t! he images in varying external magnetic fields proves that MTXM is a highly adapted tool to investigate nanostructured magnetic systems. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A multilayered FeGd system sputtered on a Si[sub 3]N[sub 4]-membrane was used to demonstrate that magnetic transmission x-ray microscopy enables the imaging of the domain structure with high resolution in a quantitative way and in varying external magnetic fields. The field-dependent evolution of sub-100 nm out-of-plane magnetized domains, i.e., the transition from stripe into bubble domains, could be observed in detail. It has been shown that critical fields like the bubble collapse field can be described by a wall energy model. Contrary to the assumption of the theory, the magnetization does not remain perpendicular to the film plane in all cases. This is only true inside the bubbles. In the stripe domains the magnetic moments rotate. Their angle could be measured as a function of the external applied field. Internal stray fields can cause a rotation of moments leading to a contrast at the edges of stripe domains. The results indicate that the magnetization reversal in 3d/4f multilayers is not only determined by wall motions and is therefore more complex than previously assumed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In order to study sub-100-nm domains in magnetic multilayers a combination of three high-resolution imaging techniques has been applied to the same samples for the first time: magnetic force microscopy (MFM), Lorentz microscopy with a transmission electron microscope, and magnetic transmission x-ray microscopy (MTXM). The samples—atomically stacked [Fe(001)/Au(001)][sub n] multilayers with an approximate L1[sub 0]-lattice—were prepared by molecular beam epitaxy (MBE) on a GaAs(001) substrate which was then locally removed by laser-induced wet etching to create a window that is transparent for 200 keV electrons and soft x-rays. Magnetization curves with perpendicular and in-plane applied field indicate a spontaneous perpendicular magnetization with an equilibrium domain pattern in small fields and reversible wall motion. About 60 nm wide domains could be observed with MFM and MTXM, respectively. Lorentz images did not show any in-plane magnetic contrast, but the domain pattern appeared when the sample was tilted. This indicates that the magnetization is indeed strictly perpendicular. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

X-ray magnetic circular dichroism (X-MCD) was used as a large, element-specific and quantitative magnetic contrast mechanism in the soft X-ray microscopes at BESSY I (Berlin) and the ALS (Berkeley). The present state and potential of magnetic transmission X-ray microscopy (MTXM) is outlined. The possibility to record images in varying magnetic fields and the high spatial resolution down to 25 nm were used to image out-of-plane magnetized (4 ÅFe / 4 ÅGd)×75 systems. Magnetic domains could be studied in arrays of circular and square dots with lateral dimensions down to 180 nm. Hysteresis loops of individual dots were deduced using the direct proportionality of the X-MCD contrast to the sample magnetization. Images of a 3 nmCr / 50 nmFe / 6 nmCr film demonstrate for the first time that MTXM is also able to observe in-plane magnetized domains. In the future the possible applications of MTXM will be extended with regard to the strength of the external field, the available energy range and the sample conditions by building a dedicated transmission X-ray microscope for magnetic imaging at BESSY II. [ABSTRACT FROM AUTHOR]

The combination of magnetic circular dichroism as a magnetic contrast mechanism and a transmission x-ray microscope allows imaging of magnetic structures with lateral resolutions down to 25 nm. Results on magneto-optical Tb[sub 25](Fe[sub 75]Co[sub 25])[sub 75] layers system with thermomagnetically written bits of various sizes were obtained at the x-ray microscope XM-1 at the Advanced Light Source in Berkeley, CA. The results prove the thermal stability of the bits in the recording process. Furthermore the capability of soft x-ray microscopy with respect to the achievable lateral resolution, element specificity and sensitivity to thin magnetic layers is demonstrated. The potential of imaging in applied magnetic fields for both out-of-plane and in-plane magnetized thin magnetic films is outlined. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]