A Focus on Magnetism and Magnetic Materials
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The following series of articles aims at conveying the excitement and vitality of current work in magnetism and magnetic materials. desired characteristics. D.T. Pierce, J. Unguris, and R.J. Celotta describe a newly developed technique for highresolution imaging of domains. Designated scanning electron microscopy with polarization analysis (SEMPA), the method also produces a topographic image of the same region. This dual ability to measure simultaneously both the physical and the magnetic structure makes SEMPA a powerful analytical tool. Its capabilities have been demonstrated on a variety of Systems, and there is little doubt that SEMPA will become increasingly important in magnetic materials research. Enormous recent attention has centered on the new ceramic superconductors because of their high superconducting transition temperatures (Tc). In his article, S.K. Sinha incisively conveys the important role magnetism plays in the physics of these fascinating materials. Our understanding of the basic superconducting mechanism and the spectacularly high Tc's will evolve inevitably
with a concomitant understanding of the relevant magnetic interactions and the nature of the magnetic states. Grown and studied with ultrahigh vacuum techniques, epitaxial magnetic metal films have helped create the entirely new subfield of surface and interfacial magnetism. G.A. Prinz reviews the exciting results which have emerged from this increasingly active area. Thin single-crystal films of higher quality and purity than their bulk analogs have been prepared, raising fundamental questions regarding such issues as the magnetic character of a surface and surface anisotropy. Furthermore, completely new materials, including magnetic superlattices, are being formed by epitaxial growth methods. They are also expanding our basic k n o w l e d g e and offer significant promise for eventual technological application. N. Samarth and J.K. Furdyna discuss diluted magnetic semiconductors and the profound physical effects which can occur when magnetic ions are substituted into certain semiconducting alloys. Among the unusual, intriguing phenomena are immense Faraday rotation, giant negative magnetoresistance, and metal-insulator transitions induced by an external magnetic field. Opportunities for practical application of these materials are numerous and have only begun to be tapped. A new era in permanent magnet technology has commenced with the development of neodymium-iron-boron materials featuring excellent magnetic properties and potential economic advantages. J.J. Croat and I describe the novel ternary Compound, Nd2Fe14B, central to this area and go on to discuss the preparation of practical magnets via the rapid solidification technique of melt spinning. Although Nd2Fe]4B was discovered only a few years ago, commercial production of Nd-Fe-B magnets is already under way. It is a genuine pleasure to acknowledge the time, energy, and enthusiasm of the authors in preparing this series. I am confident that the reader will find the articles instru
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