Goodenough, John B.

Scope and Contents Project Whirlwind Controlled Distribution Memo 6D-103. A mechanism is proposed to show how the Fermi surface interacts with the Brillouin zone boundaries. The direction and relative magnitude of the variation of the c/a ratio for hexagonal crystals from the ideal value for close packing are predicted as a function of the electron-atom ratio, and these predictions are compared with values of lattice parameters which are reported in the literature. Reprinted from The Physical Review, Vol. 89,...

Scope and Contents MIT DIC 6889. Project Whirlwind Memo 6M-3185. Semicovalence and its effects on indirect magnetic-exchange interaction are reviewed and applied to the manganites. These considerations lead to qualitative predictions which are in complete accord with the following experimentally observed facts, where x is taken as the percentage of manganese ions which are Mn[superscript 4+]: (1) At x = 0, LaMnO₃ is an orthorhombic perovskite-type lattice with a₁ = a₃ > a₂. The ratio a₂/a₃ increases to 1 at...

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MIT DIC 6889. Project Whirlwind Memo M-1929. The undersigned continued the discussion on FeNi₃ initiated by Dudley Buck at the seminar on magnetism, the meaning of order-disorder and entropy were examined. Hysteresis loops, saturation magnetization and Curie point of ordered and disordered states were contrasted and their differences tentatively explained.

Scope and Contents MIT DIC 6889. Project Whirlwind Memo M-2473. A mechanism is proposed whereby a tetragonal 2MOMnO₂ phase is precipitated at {101} surfaces in manganese-rich spinel systems. The critical Mn[superscript +4] content for precipitation is estimated from studies of lattice parameters in the Fe₃O₄-Mn₃O₄-ZnMn₂O₄-ZnFe₂O₄ system. A prediction is then made as to which compositions in the MgO-Fe₃O₄-Mn₃O₄ system will give favorable B-H loops. A large region is found to depend critically upon the firing...

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MIT DIC 6889. Project Whirlwind Memo 6M-3215. The eighteen papers which were presented at the conference on ferrimagnetism at the U. S. Naval Ordnance Laboratory, 11-12 October 1954, are summarized. Pertinent discussions are also included.

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MIT DIC 6889. Project Whirlwind Memo M-2649. A graphical summary of some of the magnetic data which were collected during 1953 on the MgO-Fe₂O₃-MnO System is presented.

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MIT DIC 6889. Project Whirlwind Memo M-2234. This memo is a summary of a Group 63 seminar on magnetism. Topics include a paper presented at the 1953 Spring meeting of The American Physical Society by C. L. Hogan.

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MIT DIC 6889. Project Whirlwind Memo M-1926. This memo is a summary of a Group 63 seminar on magnetism. Topics include evaluation of the density of energy states at the top of the Fermi distribution, and binding energies in body-centered transition metals.

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MIT DIC 6889. Project Whirlwind Memo M-1933. This memo is a summary of a Group 63 seminar on magnetism. Topics include Heusler alloys, the Heisenberg model, the Zener model, the Heisenberg theory of ferromagnetism, and the collective electron theory based on the Hartree self-consistent field method.

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MIT DIC 6889. Project Whirlwind Memo M-1951. This memo is a summary of a Group 63 seminar on magnetism. Topics include ferrimagnetic properties of ferrites and the mechanism of spin reversal in domain wall motion. Professor N. Bloembergen of the Department of Physics, Harvard university, was guest speaker at the seminar.

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MIT DIC 6889. Project Whirlwind Memo M-1914. This memo is a summary of a Group 63 seminar on magnetism. Topics include the phenomenon of superexchange, Hund's rule, the exchange effect, ferrites, and ferrimagnetism.

Scope and Contents MIT DIC 6889. Project Whirlwind Engineering Note E-532. The critical requirements for a ferromagnetic memory core are reviewed. Domains of reverse magnetization must form and grow within a core if its induction is to be reversed. The nature of the nucleation centers for these reverse domains will affect the shape of the hysteresis loop and the switching time. Inclusions, grain boundaries, and crystalline surfaces are analyzed as lattice imperfections which could act as nucleating centers. It...

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Division 6 Memo M-4064. Memorandum discussing domain patterns in BiMn and SiFe alloys.

Scope and Contents Division 6 Memo M-4328. The factors which influence the shape of the B-H loop, the coercivity, the permeability, and the flux reversal time in ferrimagnetic spinels are considered on two levels: a macroscopic and an atomic level. To minimize consideration of shape-dependent properties, the ferrite components are assumed to be toroids. With the assumption that domain walls are present in the material, the influence of grain-boundary magnetic poles on B-H loop shape, coercivity, permeability...

Scope and Contents MIT DIC 6889. Project Whirlwind Memo M-3059. After a short discussion of the factors which influence the incremental permeability, three different methods are discussed which should give a large change in incremental permeability with a change of the biasing field. The first requires a grain-oriented magnetic tape and take advantage of demagnetizing fields. The second requires a material with a square B-H loop, a low coercive force, and a large maximum permeability. The third requires a...

Scope and Contents MIT DIC 6889. Project Whirlwind Memo M-2629. The ferrite single-crystal-synthesis program of the Bell Telephone Laboratories was investigated. Information on some experimental techniques for measurement about to be undertaken in this laboratory was also obtained. Galt reported some recent work on microwave resonance in nickel ferrite which suggests a general technique for the measurement of the heat of activation for various electron-transfer relaxation phenomena. A brief outline is given to...