Arthur von Hippel and Magnetism
- PDF / 349,860 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 47 Downloads / 208 Views
Arthur von Hippel and Magnetism John B. Goodenough Abstract This article examines the role that Arthur von Hippel played in magnetism work in the 1950s. Von Hippel understood that the ferrimagnetic insulators represented by the ferrospinels, magnetoplumbites, and ferrogarnets were critical for the high-frequency technology that was being developed after World War II. At the Laboratory for Insulation Research at MIT, he and his students concentrated on the response of these materials to electric and magnetic excitations over a wide frequency range that extended, with gaps, from dc to the ultraviolet. For magnetic studies, he used microwave frequencies to obtain resonance and relaxation data that could be interpreted because the magnetic spins are relatively loosely coupled to their surroundings. He supplemented these resonance studies with classical magnetometer, transport, and x-ray diffraction measurements on single-crystal samples in order to obtain fundamental information that would aid in the design of materials for technical applications. Keywords: Arthur von Hippel, magnetism.
Introduction During World War II, Arthur von Hippel established the Laboratory for Insulation Research at the Massachusetts Institute of Technology, where he performed his pioneering work on BaTiO3 and other ferroelectrics. During that same period in Europe, J.L. Snoek and collaborators at the Philips Research Laboratories in Eindhoven, L. Néel with E.F. Bertaut and R. Pauthenet at the Institut Fourier in Grenoble, and C. Guillaud in Paris were quietly working on the ferrospinels MFe2O4, where M is a divalent cation. Trivalent cations or M(IV) M(II) pairs were also substituted for Fe(III). Many of these spinels were ferrimagnetic insulators of interest for high-frequency applications such as microwave devices, magnetostrictive transducers, and magnetic memory cores. It was therefore natural that the Laboratory for Insulation Research under von Hippel should shift some activity from ferroelectric to ferromagnetic oxides in the 1950s. During this period, the advent of nuclear reactors, which can provide a beam of neutrons, made possible neutron diffraction and therefore the direct determination of atomic magnetic order below the Curie temperature TC , a development that would transform the study of magnetic materials. Moreover, the discovery of the hexagonal magneto-
MRS BULLETIN • VOLUME 30 • NOVEMBER 2005
plumbites (xBaO•yFe2O3•zMO) exhibiting a large magnetocrystalline anisotropy useful for hard (permanent) magnets and the low-loss ferrogarnets R3Fe5O12 (R rare earth or yttrium) added to the intense international activity in this field, a field that brought together engineers, physicists, and chemists/ceramists to understand better how to design materials that would enable a variety of new technologies. In this way, the field proved an incubator for the development of a cadre of scientists who would help to create the field of materials science and engineering that we know today. The A[B2]O4 spinel structure is illustrated in Fi
Data Loading...
