Richard M. Bozorth

Bio: Richard M. Bozorth is an academic researcher from Bell Labs. The author has contributed to research in topics: Magnetization & Magnetic shape-memory alloy. The author has an hindex of 24, co-authored 50 publications receiving 2791 citations.

Anisotropy and Magnetostriction of Some Ferrites

Abstract: Magnetic crystal anisotropy and magnetostriction have been measured in various single crystals of ferrites having compositions represented approximately by $M{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$, where $M$ stands for Mn, Fe, Co, Ni, and Zn in various proportions. Special attention is given to heat-treatment in a magnetic field.The magnetic anisotropy of cobalt ferrite at room temperature is as high as 4\ifmmode\times\else\texttimes\fi{}${10}^{6}$ ergs/${\mathrm{cm}}^{2}$. Magnetostriction is as high as 800\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$. Magnetic anneal is effective at temperatures as low as 150\ifmmode^\circ\else\textdegree\fi{}C, and causes the hysteresis loop to become square. In polycrystalline material the response to magnetic anneal is a maximum at compositions intermediate between Co${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$ and ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$.The constants for the various specimens are tabulated. Values of the anisotropy constants of Mn${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$ at 20\ifmmode^\circ\else\textdegree\fi{}C and -196\ifmmode^\circ\else\textdegree\fi{}C are the same as those determined from ferromagnetic resonance experiments. At -196\ifmmode^\circ\else\textdegree\fi{}C the constant for ${\mathrm{Ni}}_{0.75}$${\mathrm{Fe}}_{2.25}$${\mathrm{O}}_{4}$ differs markedly from that determined by ferromagnetic resonance; this is to be expected from the relaxation phenomena observed by Galt, Yager, and Merritt.

Magnetic Domain Patterns on Single Crystals of Silicon Iron

Abstract: Magnetic powder patterns have been obtained on electrolytically polished surfaces of single crystals of iron containing 3.8 weight percent silicon. Domains are easily visible, outlined by accumulations of colloidal magnetic particles. Several techniques have been developed that enable the direction of magnetization in each domain to be determined. Many types of domain patterns are observed, depending on the orientation of the surface with respect to the crystal axes. The simpler patterns can now be interpreted in some detail, and support the idea that the internal domain structure is relatively simple and is usually composed of a series of plates or slabs magnetized at 45\ifmmode^\circ\else\textdegree\fi{} or 90\ifmmode^\circ\else\textdegree\fi{} to the plate length. In one case it is verified that the plate thickness depends on plate length in approximate accordance with theory; and, for the more complicated "tree" patterns, comparison of theory with experiment shows that good agreement can be obtained using theoretical values of the wall energy. Further verification of the theory of Bloch walls is obtained by determining from experiment the change in spin orientation on traversing the wall.

Magnetic Properties of Some Orthoferrites and Cyanides at Low Temperatures

Abstract: The magnetization of some rare-earth orthoferrites and related compounds, and of some iron-group cyanides, has been investigated at temperatures between room temperature and 1.3\ifmmode^\circ\else\textdegree\fi{}K. Some are ferromagnetic, some antiferromagnetic, and some paramagnetic following the Curie-Weiss law.The compounds GdV${\mathrm{O}}_{3}$, GdFe${\mathrm{O}}_{3}$, and ErFe${\mathrm{O}}_{3}$ are apparently antiferromagnetic with N\'eel points of 7.5\ifmmode^\circ\else\textdegree\fi{}, 2.5\ifmmode^\circ\else\textdegree\fi{}, and 4.5\ifmmode^\circ\else\textdegree\fi{}K, respectively. Ordering of the Gd and Er ions at low temperatures is indicated. The compounds NdFe${\mathrm{O}}_{3}$, SmFe${\mathrm{O}}_{3}$, YFe${\mathrm{O}}_{3}$, NdV${\mathrm{O}}_{3}$, PrV${\mathrm{O}}_{3}$, and SmV${\mathrm{O}}_{3}$ show a rapid rise in ferromagnetic moment as the temperature is lowered below about 15\ifmmode^\circ\else\textdegree\fi{}K. GdTi${\mathrm{O}}_{3}$ is ferromagnetic with 0.54 Bohr magneton per molecule.Many of the cyanides of type $A(B{\mathrm{C}}_{6}{\mathrm{N}}_{6})$ are ferromagnetic with magnetic moments of 1 to 4 Bohr magnetons per molecule and Curie points of 3 to 50\ifmmode^\circ\else\textdegree\fi{}K.A null method of measurement is used. Movement of a pendulum in a field gradient is detected with strain gauges and balanced with a coil. In the space containing the specimen and the balancing coil the gradient varies linearly with distance.

Texture analysis

Abstract: This chapter reviews and discusses various aspects of texture analysis. The concentration is o the various methods of extracting textural features from images. The geometric, random field, fractal, and signal processing models of texture are presented. The major classes of texture processing pro lems such as segmentation, classification, and shape from texture are discussed. The possible applic tion areas of texture such as automated inspection, document processing, and remote sensing a summarized. A bibliography is provided at the end for further reading.

Anisotropic magnetoresistance in ferromagnetic 3d alloys

Abstract: The anisotropic magnetoresistance effect in 3d transition metals and alloys is reviewed. This effect, found in ferromagnets, depends on the orientation of the magnetization with respect to the electric current direction in the material. At room temperature, the anisotropic resistance in alloys of Ni-Fe and Ni-Co can be greater than 5%. The theoretical basis takes into account spin orbit coupling and d band splitting. Other properties such as permeability, magnetostriction, and Hall voltage have no simple relationship to magnetoresistance. Anisotropic magnetoresistance has an important use as a magnetic field detector for digital recording and magnetic bubbles. Such detectors because of their small size are fabricated using thin film technology. Film studies show that thickness, grain size, and deposition parameters play a significant role in determining the percentage change in magnetoresistance. In general, the change is smaller in films than bulk materials. Several tables and graphs that list bulk and film data are presented.

Experiments on simple magnetic model systems

Abstract: “…. For the truth of the conclusions of physical science, observation is the supreme Court of Appeal….” (Sir Arthur Eddington, The Philosophy of Physical Science.) In this paper we shall review the theoretical and experimental results obtained on simple magnetic model systems. We shall consider the Heisenberg, XY and Ising type of interaction (ferro and antiferromagnetic), on magnetic lattices of dimensionality 1, 2 and 3. Particular attention will be paid to the approximation of these model systems in real crystals, viz. how they can be realized or be expected to exist in nature. A large number of magnetic compounds which, according to the available experimental information, meet the requirements set by one or the other of the various models are considered and their properties discussed. Many examples will be given that demonstrate to what extent experiments on simple magnetic systems support theoretical descriptions of magnetic ordering phenomena and contribute to their understanding. It will a...

A room-temperature organometallic magnet based on Prussian blue

Abstract: THE rational design of molecular compounds that exhibit spontaneous magnetic ordering might enable one to tailor magnetic properties for specific applications in magnetic memory devices1–4. In such materials synthesized previously5–17, however, the underlying weak magnetic interactions are incapable of maintaining ordering at ambient temperatures. One remarkable exception is a compound derived from vanadium and tetracyanoethylene18, but the material is amorphous and fragile, and consequently the molecular interactions responsible for its striking properties are not understood. Here we demonstrate another route to the synthesis of a room-temperature organometallic magnet, in which we combine a hexa-cyanometalate [M(CN)6]q− with a Lewis acid Lp+ If L and M are transition-metal ions, then the orbital interactions in the resulting compound can be described by well understood principles21–24, and it is therefore possible to choose the metals to tune the compound's magnetic properties–in particular, the magnetic ordering (Curie) temperature Tc (refs 21–26). We have synthesized a room-temperature magnetic material (TC = 315 K) that belongs to the Prussian blue family of compounds27 (where M is chromium and L is vanadium), demonstrating that transition-metal hexacyano complexes are promising components for the construction of molecule-based high-Tc magnets.

Anisotropie magnétique superficielle et surstructures d'orientation

Abstract: Dans la premiere partie de ce Memoire, on propose de considerer l'energie magnetocristalline et magnetoelastique d'un corps ferromagnetique comme la somme de termes elementaires relatifs chacun a une liaison, c'est-a-dire a un couple de deux atomes proches voisins. Sur cette base, on developpe la theorie de la magnetostriction et de l'anisotropie magnetocristalline et, de sa comparaison avec les resultats experimentaux, on deduit les valeurs des parametres qui caracterisent l'energie de liaison. Des memes premices, on deduit qu'il doit exister dans les corps ferromagnetiques, une energie d'anisotropie superficielle, dependant de l'orientation de l'aimantation spontanee par rapport a la surface et ne presentant d'ailleurs aucun rapport avec le phenomene classique de champ demagnetisant de forme. Cette energie de surface, de l'ordre de O, I a I erg/cm2, est susceptible de jouer un role important dans les proprietes des substances ferromagnetiques dispersees en elements de dimensions inferieures a I00 A. Dans la seconde partie, on montre, en adoptant le point de vue precedent, que dans les solutions solides ferromagnetiques a deux constituants au moins, traitees a chaud dans un champ magnetique, les atomes proches voisins d'un atome donne doivent se repartir d'une facon anisotrope autour de ce dernier et donner naissance a une surstructure d'orientation. Par trempe, cette surstructure est susceptible de se conserver en faux equilibre a basse temperature et se manifeste par l'apparition d'une anisotropie magnetique de caractere uniaxial. Les phenomenes sont precises par le calcul, notamment le role de la concentration, dans le cas de differents reseaux cubiques simples et dans le cas d'une substance isotrope par compensation. L'anisotropie calculee est de l'ordre de I03 a I05 ergs/cm2, mais parait depasser largement ces valeurs dans des cas exceptionnels. Cette theorie rend compte des proprietes des ferronickels traites a chaud dans un champ magnetique et, en particulier, des monocristaux de permalloy. On suggere le role possible de ces effets dans l'alnico V et les ferrites de cobalt orientes. Dans une troisieme partie, on montre que l'on peut creer une surstructure d'orientation dans une solution solide quelconque au moyen d'une deformation elastique a chaud et la conserver par trempe. Si la solution solide est ferromagnetique, les surstructures ainsi creees donnent naissance a une anisotropie magnetique de caractere uniaxial. En s'appuyant sur une theorie sommaire des proprietes elastiques des solutions solides developpee a cet effet, le phenomene est soumis au calcul : on trouve des anisotropies de I04 ergs/cm3 pour des tensions de I0 kg/mm2 , dans le cas des ferronickels. On propose d'interpreter par la creation de telles surstructures l'anisotropie magnetique uniaxiale des ferronickels quasi unicristallins lamines a froid, la deformation plastique permettant aux atomes de prendre la repartition d'equilibre correspondant au systeme des tensions appliquees. Dans les ferronickels polycristallins lamines ou etires, l'anisotropie est de signe contraire a la precedente; on propose de l'expliquer selon le meme mecanisme que les phenomenes de restauration apres fluage.