Magnetic microstructures and their dynamics studied by X-ray microscopy (original) (raw)
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Magnetic imaging with full-field soft X-ray microscopies
Journal of Electron Spectroscopy and Related Phenomena, 2013
Progress toward a fundamental understanding of magnetism continues to be of great scientific interest and high technological relevance. To control magnetization on the nanoscale, external magnetic fields and spin polarized currents are commonly used. In addition, novel concepts based on spin manipulation by electric fields or photons are emerging which benefit from advances in tailoring complex magnetic materials. Although the nanoscale is at the very origin of magnetic behavior, there is a new trend toward investigating mesoscale magnetic phenomena, thus adding complexity and functionality, both of which will become crucial for future magnetic devices.
Element-specific imaging of magnetic domains at 25 nm spatial resolution using soft x-ray microscopy
Review of Scientific Instruments, 2001
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 25 ͑Fe 75 Co 25 ͒ 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.
Magnetic soft x-ray microscopy at 15 nm resolution probing nanoscale local magnetic hysteresis
Journal of Applied Physics, 2006
Recent progress in x-ray optics has pushed the lateral resolution of soft x-ray magnetic microscopy to below 15 nm. We have measured local magnetic hysteresis on a nanometer scale at the full-field x-ray microscope XM-1 at the Advanced Light Source in Berkeley, approaching fundamental length scales such as exchange lengths, Barkhausen lengths, and grain diameters. We have studied the evolution of magnetic domain patterns in a nanogranular CoCrPt film with a pronounced perpendicular magnetic anisotropy and revealed nanoscopic details associated with the granular film structure. From a quantitative analysis of the field-dependent magnetic domain patterns, we are able to generate local magnetic hysteresis map on a nanometer scale. Our findings indicate a significant variation of local coercive fields corresponding to the nanoscopic behavior of magnetic domains.
Journal of Applied Physics, 2006
Recent progress in x-ray optics has pushed the lateral resolution of soft x-ray magnetic microscopy to below 15 nm. We have measured local magnetic hysteresis on a nanometer scale at the full-field x-ray microscope XM-1 at the Advanced Light Source in Berkeley, approaching fundamental length scales such as exchange lengths, Barkhausen lengths, and grain diameters. We have studied the evolution of magnetic domain patterns in a nanogranular CoCrPt film with a pronounced perpendicular magnetic anisotropy and revealed nanoscopic details associated with the granular film structure. From a quantitative analysis of the field-dependent magnetic domain patterns, we are able to generate local magnetic hysteresis map on a nanometer scale. Our findings indicate a significant variation of local coercive fields corresponding to the nanoscopic behavior of magnetic domains.
X-Ray Diffraction Microscopy of Magnetic Structures
Physical Review Letters, 2011
We report the first proof-of-principle experiment of iterative phase retrieval from magnetic x-ray diffraction. By using the resonant x-ray excitation process and coherent x-ray scattering, we show that linearly polarized soft x rays can be used to image both the amplitude and the phase of magnetic domain structures. We recovered the magnetic structure of an amorphous terbium-cobalt thin film with a spatial resolution of about 75 nm at the Co L 3 edge at 778 eV. In comparison with soft x-ray microscopy images recorded with Fresnel zone plate optics at better than 25 nm spatial resolution, we find qualitative agreement in the observed magnetic structure.
Optics for element-resolved soft X-ray magneto-optical studies
Journal of Magnetism and Magnetic Materials, 1999
The status of polarizing optical elements for the vacuum ultraviolet and soft X-ray range extending from roughly 50 to 2000 eV are reviewed, as are some of their emerging applications in magneto-optical studies utilizing synchrotron radiation. The optics include tunable linear polarizers and birefringent phase retarders based on multilayer interference structures, and circular polarizing filters based on magnetic circular dichroism. Magneto-optical capabilities enabled by these optical elements include measurement of Faraday and Kerr rotation spectra and hysteresis loops, and the conversion of linear to circular polarization and helicity switching. Circular polarizers combined with scanning zone plate microscopes yield magnetization contrast in transmission imaging. Examples using these capabilities to study polycrystalline Fe films and Fe/Cr multilayers are given. Resonant soft X-ray magneto-optical spectroscopies are especially relevant to obtaining an understanding of magnetism on a microscopic level in complex materials and nanostructures because their element-specific signals can be larger than in other spectral ranges. Combined with scattering and microscopy techniques these spectroscopies can provide depth sensitive and lateral spatial resolution on the nanometer scale.
Soft X-ray microscopy to 25nm with applications to biology and magnetic materials
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001
We report both technical advances in soft X-ray microscopy (XRM) and applications furthered by these advances. With new zone plate lenses we record test pattern features with good modulation to 25 nm and smaller. In combination with fast cryofixation, sub-cellular images show very fine detail previously seen only in electron microscopy, but seen here in thick, hydrated, and unstained samples. The magnetic domain structure is studied at high spatial resolution with X-ray magnetic circular dichroism (X-MCD) as a huge element-specific magnetic contrast mechanism, occurring e.g. at the L 2,3 edges of transition metals. It can be used to distinguish between in-plane and out-of-plane contributions by tilting the sample. As XRM is a photon based technique, the magnetic images can be obtained in unlimited varying external magnetic fields. The images discussed have been obtained at the XM-1 soft X-ray microscope on beamline 6.1 at the Advanced Light Source in Berkeley. #
Japanese Journal of Applied Physics, 2000
The benefit of combining soft X-ray magnetic circular dichroism and photoelectron microscopy is demonstrated by applying this combination to the observation of the magnetic domain structures of rectangular microstructures. The size and aspect-ratio dependence of the transformation of the domain structures by magnetic field pulses is investigated. The switching mechanism, which is very important in the application to magnetic storage, is discussed in terms of transformation between saturated and vortex domain structures.