Materials Literature
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Outstanding permanent magnet properties were recently observed in a Nd-Fe-B compound which was shown to crystallize in a new phase, R2Fe14B. Polarized neutron measurements are reported on Y2Fe14B and Nd2Fe14B single crystals. The 3d Fe moment on different sites in Y2Fe14B at 4.2 K is closely related to local environme…
Photoelectron spectroscopic measurements of core-electron levels in cations of transition-series insulators commonly show ``satellite'' features in the vicinity of the ``main'' photoelectron peaks. In this paper, the relationship between main lines and adjacent satellites is systematically examined for 3d-series insul…
We report the superconductivity with the onset temperature as high as 8 K in the organic conductor of β-(BEDT-TTF) 2 I 3 , bis-ethylenedithio otetrathiofulvalene-triiodide. The increased superconducting transition temperature was achieved by an application of a soft pressure, i.e. 1.3 kb. High value of the upper criti…
Present works describe the developments the low cost R-Fe-B sintered permanent magnets. Three different didymiums are chosen for the low cost mixtures of rare-earth elements. The studied alloy compositions are Fe-(32.5–34.5)wt. %R-(1–1.6)wt. %B, where R elements are didymium (Nd-10wt. %Pr), 5Ce-didymium (Nd-15%Pr-5%Ce…
The variation of lattice parameter, saturation magnetization, and Curie temperature on the addition of Ti4+, Zr4+, and Sn4+ to some Ni-Zn ferrite compositions are reported and the results are explained on the basis of the movement of the substituting ions first to the tetrahedral and finally to the octahedral sites of…
Measurements of recombination along the tracks of 2-MeV alpha particles and 0.7-MeV protons in thermally grown silicon dioxide are presented. The results agree quite well with the columnar recombination model at applied fields above about 1 MV/cm if one assumes an initial Gaussian column radius b=3.5 nm. The agreement…
Amorphous Tb-Fe thin films have been produced by dual-gun dc magnetron cosputtering, which allows a moderate range of compositions (spanning about 20 at. %) to be deposited in a single run under identical conditions. The films exhibit clean M-H loops and torque curves which are somewhat anomalous but show consistent t…
The phonon dispersion curves of the rutile-structure compounds ${\mathrm{GeO}}_{2}$, ${\mathrm{SnO}}_{2}$, ${\mathrm{NbO}}_{2}$, and ${\mathrm{VO}}_{2}$ have been calculated in the framework of a shell model which had been used previously to reproduce the measured dispersion curves of rutile (${\mathrm{TiO}}_{2}$) rat…
We describe detailed analyses of neutron powder diffraction data on Nd2Fe14B at several temperatures and discuss relationships between the crystal structure and the magnetic properties via comparison with other rare earth-transition metal systems, Nd2Fe17 in particular. Diffraction studies have also been performed on…
A model is presented which gives a unique magnetic-field-induced transition from a two-dimensional open-orbit metal to a semimetal. A magnetic field causes the open-orbit electron motion to become progressively more one dimensional, with an effective density of states proportional to H at low field. This leads to a Fe…
Commercial rare earth metals contain several atomic % oxygen, and intermetallics synthesized using these ingredients deviate markedly from the intended compositions. In this work, high purity rare earths (<20 ppm oxygen by weight) were used. Results for R2Fe14B systems with R = Y, Nd, Sm, or Gd have been previo…
A spin reorientation occurs in Nd2Fe14B starting around Ts= 150 K. We present data on tendencies in spin reorientations in systems (Nd1−xRx)2Fe14B and Nd2Fe14−xAxB where R=different rare earths and A=Co, Al. The insensitivity of Ts to some of these substitutions appears to indicate that Nd alone is responsible for the…
Magnetic domain structures in sintered Fe-Nd-B magnets from several suppliers were studied using the polar Kerr effect. Most grains were multidomain in the thermally demagnetized state. Measurement of average surface domain width in several large grains yielded a domain-wall energy of 25 ergs/cm2 for the Fe14Nd2B prim…
A new approach to Preisach’s model which emphasizes the phenomenological nature of this model and its mathematical generality is discussed. This approach enables the formulation of necessary and sufficient conditions under which actual hysteresis nonlinearities can be represented by Preisach’s model.
Static magnetic measurements have been carried out on single crystals of Nd2Fe14B, Sm2Fe14B, and Y2Fe14B from 4.2 to 590 K. Values of K1 estimated from high field measurements at room temperature are 4.5, −12, and 1.1 MJ/m3 for Nd2Fe14B, Sm2Fe14B, and Y2Fe14B, respectively. Anisotropic behavior of the magnetization ve…
We describe calculations of the evolution of the band gap as a function of geometry in conjugated polymers based on aromatic rings: polyparaphenylene, polypyrrole, polythiophene. Our results demonstrate that the gap decreases as a function of increasing quinoid character of the backbone and is thus not minimal in the…
A new method is described which produces fully dense, well-aligned Nd-Fe-B magnets from rapidly quenched ribbons. Full density is achieved by hot pressing at ∼15 kpsi in argon at 700 °C. A second hot press in a larger die cavity to allow deformation transverse to the press direction (die upsetting) introduces a prefer…
Time-of-flight drift mobility experiments have been carried out on pure and chlorine-doped amorphous selenium films. The temperature and field dependence of the drift mobility of both types of carriers have been investigated and the charge transport mechanism has been critically examined in terms of various shallow-tr…
Time-of-flight drift mobility experiments have been carried out on evaporated films of amorphous (a-)Se 0.995 As 0.005 with chlorine as an additive up to approximately 70 at.ppm; drift mobility has been measured as a function of temperature at various applied fields. It is shown that shallow hole traps at approximatel…
ABSTRACT The deposition of scale in the near-wellbore formation and production string can result in a significant decrease in well capacity. Correctly designed scale inhibitor squeezes can successfully prevent scale deposition and the corresponding productivity declines. However, inadequate knowledge of the chemistry…