Magnetic imaging with full-field soft X-ray microscopies (original) (raw)
Related papers
Magnetic microstructures and their dynamics studied by X-ray microscopy
Micron, 2006
Full-field soft X-ray microscopy in combination with X-ray magnetic circular dichroism as contrast mechanism is a powerful technique to image with elemental specificity magnetic nanostructures and multilayered thin films at high lateral resolution down to 15 nm by using Fresnel zone plates as X-ray optical elements. Magnetization reversal phenomena on a microscopic level are studied by recording the images in varying external magnetic fields. Local spin dynamics at a time resolution below 100 ps can be addressed by engaging a stroboscopic pump-and-probe scheme taking into account the time pattern of synchrotron storage rings. Characteristic features of magnetic soft X-ray microscopy are reviewed and an outlook into future perspectives with regard to increased lateral and temporal resolution is given.
Advances in nanomagnetism via X-ray techniques
Journal of Magnetism and Magnetic Materials, 2006
This report examines the current status and the future directions of the field of nanomagnetism and assesses the ability of hard X-ray synchrotron facilities to provide new capabilities for making advances in this field. The report first identifies major research challenges that lie ahead in three broadly defined subfields of nanomagnetism: confined systems, clusters and complex oxides. It then examines the relevant experimental capabilities that are currently available at hard X-ray synchrotron light sources, using the Advanced Photon Source (APS) at Argonne as an example. Finally, recommendations are made for future development in X-ray facilities that will enhance the study of nanomagnetism, including new experimental directions, modifications that would enable in situ sample preparation, and measurements at high magnetic fields and/or low temperatures. In particular, in situ sample preparation is of high priority in many experiments, especially those in the area of surface magnetism. r
X-Ray Magnetic Circular Dichroism Picks out Single-Molecule Magnets Suitable for Nanodevices
Advanced Materials, 2009
The encoding of magnetic information at the molecular level finds in Single Molecule Magnets (SMM) a most promising avenue. SMM are composed of discrete metal-ion clusters which assemble into molecular crystals and offer unparalleled chemical flexibility and processability among soft magnetic materials. Their ground state has a large spin value and an easy-axis magnetic anisotropy, so that at low temperature the reversal of the molecular magnetic moment is subject to an energy barrier which can be overcome either via thermal activation or by a quantumtunneling mechanism. Each molecule in the crystal thus behaves as a nanometer-sized magnet, displaying hysteresis and fascinating quantum effects. Applications of SMM in ultrahigh-density information storage and spintronics are foreseen, which entail SMM organized into addressable layers at surfaces or incorporated into metal-molecule-metal junctions. However, fundamental aspects related to the magnetic behavior of SMM in these environments have not yet been fully explored. In fact, the spin dynamics of SMM is exceedingly sensitive to structural deformations, intermolecular interactions, and to other environmental effects, which are expected to be different for SMM hosted in a crystalline lattice, assembled into an addressable layer or incorporated in a metal-molecule-metal junction. Recently we have reported a magneto-optical investigation on the archetypal SMM, the mixed-valence Mn 12 complex, in different environments showing the disappearance of magnetic hysteresis when the clusters are organized as a SAM on gold. Further studies are necessary to assess if the slow magnetization dynamics that characterizes SMM behavior is compatible with the surface environment. With this goal in mind we have used X-ray magnetic circular dichroism, XMCD, at sub-Kelvin temperatures to investigate the surface magnetic properties of thin films made of two different SMM. We show here that SMM behavior is indeed observable for the first monolayer(s) but, surprisingly, not in the case of the widely investigated Mn 12 clusters.
ferrimagnetic alloys are extensively studied for their unique magnetic properties leading to possible applications in perpendicular magnetic recording, due to their deterministic ultrafast switching and heat assisted magnetic recording capabilities. On a prototype ferrimagnetic alloy we demonstrate fascinating properties that occur close to a critical temperature where the magnetization is vanishing, just as in an antiferromagnet. From the X-ray magnetic circular dichroism measurements, an anomalous 'wing shape' hysteresis loop is observed slightly above the compensation temperature. This bears the characteristics of an intrinsic exchange bias effect, referred to as atomic exchange bias. We further exploit the X-ray magnetic linear dichroism (XMLD) contrast for probing non-collinear states which allows us to discriminate between two main reversal mechanisms, namely perpendicular domain wall formation versus spin-flop transition. Ultimately, we analyze the elemental magnetic moments for the surface and the bulk parts, separately, which allows to identify in the phase diagram the temperature window where this effect takes place. Moreover, we suggests that this effect is a general phenomenon in ferrimagnetic thin films which may also contribute to the understanding of the mechanism behind the all optical switching effect.
Magnetic Properties: From Traditional to Spintronic
Springer Handbook of Electronic and Photonic Materials, 2017
This chapter reviews basic concepts used in the traditional macroscopic magnetism in order to understand current and future developments of submicronic spin-based electronics where interplay of electronic and magnetic properties is crucial. Traditional magnetism is based on macroscopic observation and physical quantities are deduced from classical electromagnetism. Physical interpretations are usually made with reference to atomic magnetism where localized magnetic moments and atomic physics prevail, despite the fact that standard ferromagnetic materials such as Fe, Co, and Ni are not localized-type magnets (they have extended s and localized d electronic states). While this picture might be enough to understand some aspects of traditional storage and electromechanics, it is no longer sufficient for the description of condensed matter systems with smaller length scales progressing toward the nanometer range. The precise nature of magnetism (localized, free, or itinerant like Fe, Co, and Ni transition metals) with simultaneous presence of charge and spin of carriers should be considered. In addition, when we deal with thin films or multilayers as in conventional electronics or with reduced dimensionality objects such as wires, pillars, dots, or grains, magnetic properties are expected to be different from three-dimensional conventional bulk systems.
Imaging magnetic domains with the X-ray dichroism photoemission microscope
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994
Few techniques are available to create images of magnetic domain structures at surfaces, due to the weakness of magnetic forces and the relative inefficiency of electron spin-detectors . We have introduced a new method for high-resolution mapping of magnetic domains, that measures the local magnetic moment and magnetization direction of individual elemental constituents of the sample . In addition, it is able to probe the magnetic properties of layers buried as much as 100 X below the surface. The method uses the magnetic X-ray dichroism effect, in combination with the X-ray photoelectron emission microscope (X-PEEM), also called the X-ray secondary-electron microscope (XSEM) . The principles involved in imaging magnetic domains using an X-ray photoelectron emission microscope are discussed, based on recent results using circularly polarized soft X-rays. Examples of applications of the technique include direct mapping of the oscillatory exchange coupling in transition metal sandwich structures, and imaging of recorded bit patterns in magnetic media. New results from perpendicular recording media are presented.