One of the first samples analyzed by Castaing in his electron probe microanalyzer (EPMA) some 50 years ago was an iron meteorite. The Widmanstatten pattern microstructure of iron meteorites can be observed at very low magnifications ( Fig. 1). These meteorites are ideal samples for microanalysis because of the Ni gradient which extends over 10 to 1000 microns in the parent taenite phase of these Fe-Ni samples (Fig. 3). The Ni gradient is the result of very slow cooling of the iron meteorite, in terms of millions of years, within a parent'asteroid.

The scanning electron microscope (SEM) has been used to characterize the microstructure of meteorites, as well as samples from the moon and mars. For example, the microstructure of the dark etching taenite areas (T in Fig. 1) of the Carleton iron meteorite is shown in Fig 2. In this example, precipitates are observed along original martensite laths which form during the cooling of the iron meteorite at low temperatures.

The steady evolution of computer controlled electron microscopes is dramatically changing the way we teach microscopy. For today’s microscopy student, an electron microscope may be just another program on the desktop of whatever computer platform he or she uses. This is reflected in the use of the term Desktop Microscopy. The SEM in particular has become a mouse and keyboard controlled machine, and running the microscope is not very different from using a drawing program or a word processor. Transmission electron microscopes are headed in the same direction.

While one can debate whether or not it is wise to treat an SEM or a TEM as just another black-box computer program, it is a fact that these machines are here to stay, which means that microscopy educators must adapt their traditional didactic tools and methods. One way to bring electron microscopes into the classroom is through the use of remote control software packages, such as Timbuktu Pro or PC-Anywhere. The remote user essentially opens a window containing the desktop of the microscope control computer and has all functions available. On microscopes with specialized graphics boards, integration of the image and control display for remote operation may not be straightforward, and often requires the purchase of additional graphics boards for the remote machine.

Light and electron microscopy are exceedingly versatile disciplines having many applications in pharmaceutical research. Many corporate and university facilities are organized with a centralized microscopy laboratory that serves the needs of many different investigators. This is also true at the Novartis Pharmaceuticals Corporation in East Hanover, New Jersey. A centralized microscopy laboratory is not only more efficient, but also most cost effective. The microscopy lab at Novartis is designed to meet the needs for a wide range of applications serving all of Research and Development. The lab contains seven functional areas for microscopy applications. A large preparation and processing area, necropsy, microtomy, TEM, SEM, wet and dry dark rooms, and an image analysis suite including telepathology, complete the lab.

Microscopy service is widely used in Pathology, Toxicology, Drug Discovery, Technical Research and Development, Production and Quality Assurance, and Compliance. Microscopy services have also been involved in marketing (packaging labels and commercials) for Novartis products.

The High Temperature Materials Laboratory (HTML, Fig. 1) is a national resource for materials characterization sponsored by the Department of Energy’s Office of Transportation Technology, Assistant Secretary for Energy Efficiency and Renewable Energy. The HTML comprises six principal user centers: Materials Analysis, Thermophysical Properties, X-ray and Neutron Diffraction, Mechanical Characterization and Analysis, Residual Stress, and Machining and Inspection Research. Instruments available at the user centers have extensive capabilities for characterizing the microstructure, microchemistry, and physical and mechanical properties of materials over a wide range of temperatures. Details of all the capabilities of the various user centers are available on the World Wide Web at http://www.ms.ornl.gov/htmlhome/default.htm.http://www.nice.org.uk/page.aspx?o=43210

To date, more than 300 different institutions, evenly divided between university and industry, have formal research agreements with the HTML. Three separate programs are available to meet the needs of these users as well as those from federal agencies wishing to gain access to the HTML.

The Analytical Instrumentation Facility (AIF) is a laboratory composed of scientists and engineers specializing in the development and application of advanced techniques for materials characterization (http://spm.aif.ncsu.edu/aif/index.html)http://www.nice.org.uk/page.aspx?o=43210. AIF facilities include an extensive collection of analytical instrumentation utilized in teaching, research, and in support of academic and industrial programs. General forms of analysis include: electron, ion, and photon microscopies, surface science and analysis, and scanned probe microscopies. An abbreviated listing of AIF capabilities follows: metallography/sample preparation, optical microscopy, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Secondary Ion Mass Spectroscopy (SIMS), Secondary Electron Microscopy (SEM), Scanned Probe Microscopy (SPM), Micro-Raman Spectroscopy, Focused Ion Beam Micro-machining (FIBM), Auger Electron Spectroscopy (AES), and X-Ray Photoelectron Spectroscopy (XPS or ESCA).

AIF is a resource utilized not only by those within NC State requiring analytical services, but also by a large number of North Carolina non-profit and industrial organizations as well as the Materials Community at large.

In addition to dinosaur bones and gem collections, the American Museum of Natural History (AMNH) is also home to nine academic research departments: Anthropology, Herpetology, Mammalogy, Earth and Planetary Sciences, Ichthyology, Ornithology, Entomology, Invertebrates, and Vertebrate Paleontology. Each of these departments supports curators, research scientists and assistants, graduate students, and post-docs engaged in a broad spectrum of research activities.

The Core Microscopy Facility houses a state-of-the-art Cold Field Emission SEM equipped with an energy dispersive x-ray spectrometer. This instrument is extremely versatile, as it must be in order to meet the challenges of a diverse imaging and microanalytical environment. Our applications run the gamut from high-resolution electron imaging of insect parts to quantitative x-ray microanalysis of 5 billion-year-old meteorites.

Mineral scientists, archeologists, anthropologists, and artifact conservators use X-ray microanalysis extensively at the AMNH. Current projects include the analysis of chondrites (meteorites that condensed at the same time as the solar system), Neolithic pottery remains, and pigment fragments from Native American artwork.

The Materials Microcharacterization Collaboratory (MMC), a pilot project of the DOE2000 program, links DOE-sponsored electron microscope user facilities at ANL, LBNL, ORNL and UIUC with that at NIST to form one collaboratory. The MMC brings the microcharacterization and microanalysis tools available in these national centers to geographically-dispersed researchers working in industries,universities, and government laboratories. It enables remote users to share on-line the instrumentation, knowledge and expertise available at the individual facilities making up the collaboratory.

On-line services available to users of the MMC may be classified as instrument, computational, and exchange services (fig. 1). LBNL's contribution to the MMC's instrumentation includes a Kratos EM-1500 HVEM (for remote in-situ high-voltage microscopy) and a Philips CM300 HREM (remote highresolution capability). DeepView is an exchange service that provides a common graphical userinterface (GUI) for control of MMC instruments over the wide area network (both the client and server sides of DeepView are available for download).

Magnetic elements in the micron and sub-micron size range are important for application as discrete bits in high density storage systems and as the active part of ultra-small magnetic sensors of the kind required in read heads. Patterning techniques based around electron beam lithography are used to fabricate elements with different sizes and shapes and TEM allows the magnetisation distributions they support to be investigated. Figure 1 shows a regular domain structure in a rectangular element of length 1μm. Of particular importance is the ability to observe directly how the elements respond to an applied field and thereby to gain information on magnetisation processes. When the fields required are in excess of a few 100 Oe, it is most convenient to use the vertical field of the objective lens. Field components in the specimen plane are then generated by tilting. For this technique to be effective it must be possible to choose an objective field strength appropriate to the elements under study and to have separate non-immersion lenses (Lorentz lenses) as the primary imaging or probeforming components.

Nondestructive evaluation of steels is both an important engineering need and a scientific challenge. Recent advances include a SQUID imaging technique that is capable of detecting small changes in stray fields at reasonable spatial resolution. The technique is motivated by the fact that the stray fields, determined by the underlying domain configurations in the material, would provide insight into the microstructure including defects, provided the interactions between the microstructure and the domain walls can be well understood.Initial work is being carried out on 1018 low-carbon steels, plastically deformed in a controlled fashion, with the goal of correlating SQUID images with magnetic domain images measured by Lorentz microscopy in a TEM.

Experiments were carried out in a CM200 FEG TEM using the OL field in low-mag (LM) mode, based on a procedure described by Verbist et al [1] and Daykin et al [2].

The new JEOL 3000F high resolution electron microscope at BNL has been optimized for Lorentz imaging. The necessary field-free environment around the sample is obtained by switching off the objective lens in the free-lens control mode, and the associated reduction in magnification is compensated for by a Gatan post-column image filter (GIF) at ∼ 20x magnification. Fresnel imaging is obtained by defocusing with objective mini-lens (OM). The use of low angle diffraction with an aperture located at the back focal plane makes it possible to obtain Foucault images.

In-situTEM dynamic magnetizing experiments combined with Lorentz magnetrc microscopy both in Fresnel and Foucault modes were used to characterize the magnetic structure of some hard and relatively soft magnets, Nd13.75Fe80.25B6 and Pr13.75Fe80.25B6, prepared by different processing routes. The goal of these in-situexperiments was to develop a reliable and effective procedure to search for, identify, and classify the different pinning centers present in real magnets that accord with their “pinning power” versus applied magnetic field.

In the last decade since its development, magnetic force microscopy[l] has emerged as a workhorse in imaging magnetic structures at the sub-micron length scales. It possesses the desirable attributes of robustness, straightforward implementation and a fairly well characterized image contrast formation. In recent years, we have successfully implemented MFM in the presence of a highly controlled external magnetic field.[2] Using this technique, it is possible to follow the sample’s magnetic evolution at various points along it’s magnetization curve. Further, by using standard software implementation, the images can be presented as an animation of the micromagnetic process. We applied this technique to study a variety of slow varying dynamics of magnetic systems, including the dc erasure of thin film recording media[3], the mechanisms of moment rotation and reversal, and the domain wall motion nanostructured magnetic elements[4,5].

In this talk, I will review the rudiments of the technique and show the “dynamics” of the magnetization of cobalt and Permalloy alloys interacting with external fields.

Tremendous progress has been made in the field of magnetic materials research and technology over the past few years. Superior properties and novel scientific questions arise due to our ability to either synthesize artificial structures or to tailor microstructures at the appropriate length scales. Microstructure, generally defined as the morphological arrangement of crystallites with similar or different phase constitutions and of the crystal defects, is controlled by the processing, which in turn affects the phases present, their topology and their dispersion. There are two key length scales that determine the magnetic behavior of materials. One is the characteristic length scale associated with the dimensional characteristics of the magnetic phenomenon under consideration. The second is the size of the microstructural feature of interest - grain size, shape, isolation, interfaces, inter-granular phases etc. It is important to identify the range where these two length scales overlap, for it is there that novel properties and phenomenon are usually observed.

Performance of permanent magnets for a variety of applications is often determined by the maximum energy product (BH)max. In order to obtain high (BH)max permanent magnetic materials have to have large coercivity. In theory the coercive field of ideally oriented, non-interacting, single domain, magnetic particles, assuming Kl is much bigger than K2, was shown to be He = 2K1/Ms - N Ms, where Kl and K2 are the magnetocrystalline anisotropy constants, Ms is the spontaneous magnetization and N is the demagnetization factor. For randomly oriented non-interacting particles the Stoner-Wohlfarth model predicts that the value of Hc decreases to about half. However, experimentally obtained values of the coercitive fields in permanent magnets are 3 to 10 and 2 times smaller for well oriented and randomly oriented samples, respectively. This discrepancy was attributed to inter-particle interaction and the microstructure of the permanent magnets. In order to understand the difference between the theoretically predicted and experimentally obtained results for He we prepared rapidly quenched, Nd-rich, NdxFe14B (2 < x < 150) ribbons.

Magnetic recording forms the basis of one of the largest international industries. Electron microscopy has of course played a significant role in relating magnetic performance to the underlying microstructure. However, relatively little attention has been paid to the ways in which imaging of the magnetic structure can be correlated with processing conditions and microstructural parameters. The present research has been aimed to address this deficiency.

A method was devised to prepare samples with large electron transparent areas (e.g., 250 microns square) from real computer hard discs. Fresnel TEM images were taken in a Philips CM20 FEG equipped with a special Lorentz pole piece, and with the objective lens off. Upon defocusing, the ferromagnetic domain structure strikingly appears. The characteristics of the recorded tracks depend on the magnetic state of the disc prior to magnetic “writing”, and much information about the local direction of magnetization could be obtained from the nature of the magnetic “ripple” structure.

Magnetic granular films, which consist of magnetic fine particles of nanometer size and a nonmagnetic matrix, have been of great interest for new magnetic materials. Their magnetic characteristics strongly depend on the fine structures, besides the combination of magnetic and nonmagnetic constituents, especially their surface topology and the particles size. Although the relationship between these fine topological structures and the macro-magnetic characteristics has been investigated systematically by many researchers, there has remained a desire to observe magnetic microstructures directly. We succeeded in observing the magnetic structure of fine particles in granular films using Lorentz microscopy.

Two kinds of specimens were observed. One was an Fe-Mo granular film. An amorphous film of Fe-Mo was prepared by dc magnetron sputtering on amorphous carbon thin films at a temperature below 180 K. The films were annealed at 770 K within an in-plane magnetic field. The other kind was an Fe-MgO granular film, where iron particles were embedded in a magnesium oxide single crystal.

Off-axis electron holography is a powerful method for providing quantitative micromagnetic structure to nanometer-scale resolution. One of the main challenges in determining magnetic induction from reconstructed phase images is the separation of phase shifts due to electrostatic and thickness effects from magnetostatic effects. We have used in-situ magnetization reversal to remove electrostatic and thickness effects which would otherwise prevent quantification of the induction. The Philips CM200-FEG microscope which was used for the holography described here is equipped with a powerful mini-lens below the specimen enabling 2nm spatial resolution (∼5nm phase resolution) and only a small residual field at the sample. In addition, the objective lens field versus current has been calibrated so that external vertical fields over a wide range of values may be applied to the sample. Tilting the sample in the presence of the vertical field has the effect of ‘applying an inplane component. This combination of high spatial resolution, quantitative analysis and in situ capabilities allows for the study of individual defects and provides experimental input for comparison with simulations.

The recent increased interest in Lorentz Microscopy methods is due to two important factors: (1) the advent of digital detection systems (CCD cameras) and advanced computer controlled transmission electron microscopes, and (2) the continually decreasing length scale of magnetic recording media and related magnetic materials. Along with the increased experimental resolution and detection sensitivity one should ask the question: how small a magnetic moment can one detect with conventional Lorentz or electron holography techniques? And, perhaps more importantly, which technique should one use to obtain the best spatial resolution? To address these questions we identified a simple model system :the uniformly magnetized sphere.

The phase of the electron wave after passing through a region with a non-zero magnetic vector potential and an internal electrostatic potential Vscan be computed from the Aharonov-Bohm trajectory integral. For a spherical particle with a uniform magnetization and a constant mean inner potential (see geometry in Fig. la), this phase shift can be analytically computed.

The shape anisotropy of a magnetic thin film competes with the easy-axis anisotropy, which gives rise to different domain structures compared to the bulk magnetic materials. Recent Lorentz microscope and electron holography and differential-phase-contrast experiments show complex domain structures with features not found in bulk materials seen by magneto-optic method.

In this report we use micromagnetic simulation techniques to study the effect of thickness on the domain structure of magnetic thin films with various orientations relative to the easy axis and compare with those in the bulk materials. The results of the simulations can be used to compare with the data obtained using electron holography experiments to give us quantitative understanding of the domain structure in hard magnetic materials.

We model the magnetic films with an array of dipoles of size 16×l6×Lz, where Lz the thickness of the sample.

Magnetic imaging can be performed both on conventional (projection) and scanning TEM (CTEM/STEM). The CTEM-based magnetic imaging, classified into Fresnel, Foucault, holography, and other modes, has proven successful by now in observing various magnetic objects, and has accordingly been well documented elsewhere. The STEMbased one has emerged relatively recently prompted by the rapid growth of current STEM technology.

The most ubiquitous implementation of Lorentz microscopy on a STEM is the differential phase contrast (DPC) mode. Each scanning signal obtained in the DPC mode is linear to Lorentz deflection, thus reflects the magnitude of an in-plane component of magnetic induction integrated along the optical axis(Fig.l). The signals therefore suffice to generate integrated in-plane magnetic induction maps(Fig.2). Furthermore, by making use of the fact that the Lorentz deflection distribution across the image plane forms an irrotational (vortex-free) 2D vector field, a pertinent numerical image processing yields a function equivalent to the electron phase function representing magnetically distorted electron wavefront.

Mulitlayers consisting of various combinations of 1-10 nm thick ferromagnetic, antiferromagnetic and nonmagnetic films have numerous applications in magnetic recording, non-volatile data storage, and sensor technologies. One key aspect to understanding how these devices work is being able to image their magnetic structure. SEMPA is well suited for this job, because of its surface sensitivity and compatibility with thin film growth and surface analysis techniques. This talk will review the SEMPA technique and describe thep use of SEMPA in two examples; one in which the magnetization is imaged while growing a multilayer, and another which examines the magnetization while depth profiling a multilayer by ion milling.

A SEMPA investigation of the magnetic exchange coupling in an Fe/Cr/Fe sandwich is shown in Figs. 1 and 2. A wedge shaped Cr interlayer was grown as shown in Fig. 1 in order to measure the Cr thickness dependence of the exchange coupling.