Strong Paramagnetism Research Articles

Electron Transport Properties of Amorphous Alloys

Emphasis was laid on the need for classifying metallic glasses into five groups in terms of their magnetic states: 1) ferromagnetism with T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> ≫ 300K, 2) weak ferromagnetism, 3) spin glass or Kondo states, 4) temperature-independent strong paramagnetism, and 5) temperature-independent weak para-or diamagnetism. The temperature dependence of the electrical resistivity in the range 10 to 300K was discussed for the respective group alloys. Only the data for group 5) metallic glasses can be consistently interpreted on the basis of the generalized Faber-Ziman theory. Nevertheless, it was shown that the 2k <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</inf> /K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> =l.0 criterion is not sufficient to predict a negative TCR even in group 5) alloys.

On the magnetic susceptibility of the liquid Pd1?x Si x alloy system at 1825 K

The isothermal magnetic susceptibility χ(x) of the completely miscible liquid Pd1−xSix alloy system shows a rapid monotonous decrease withx from strong paramagnetism to weaklyx-dependent diamagnetism. The measured susceptibility isotherm at 1825 K is analysed within 0≦x≦1 by using a semiphenomenological method of decomposing the magnetic susceptibility into its constituent parts. Because of the empirical similarity between liquid and glassy metals this interpretation also provides assertions about the magnetism of glassy Pd1−xSix aroundx=0.2.

Observation of a first-order phase transition in single-crystal ErRh4B4atHc2

Detailed magnetization curves show a first-order phase transition in single-crystal ErRh/sub 4/B/sub 4/ at H/sub c/2 for the temperature range 3.3> or approx. =T> or approx. =1.4 K when the field is parallel to the a axis, along which the crystal shows strong paramagnetism. Below 3.3 K, the discontinuity in magnetization at H/sub c/2 grows with decreasing temperature and moves to lower fields, ultimately developing into the spontaneous moment in the ferromagnetic state. In the c direction, where the crystal exhibits weak paramagnetism, the superconducting magnetization curves show ordinary type-II behavior.

Strong Paramagnetism in ZrMnCo

Strong Paramagnetism in ZrMnCo

Kontakt- und Pseudokontakt-Verschiebungen in den 1H- und 13C-NMR-Spektren des paramagnetischen Komplexes Tricyclopentadienyl-(cyclohexylisonitril)-europium(III) / Contact- and Pseudocontact Shifts in the 1H- and 13C-NMR Spectra of the Paramagnetic, Organometallic Complex Tricyclopentadienyl-(cyclohexylisonitrile)-europium(III)

The organometallic NMR shift reagent Eu(C5H5)3 induces large paramagnetic shifts in the 1H-NMR spectrum of cyclohexylisonitrile. The 1:1-adduct (C5H5)3Eu•CNC6H11 has been isolated. The dipolar nature of the paramagnetic shifts of some of the C6H11-protons in this complex is used to fractionate the shifts of the C5H5-nuclei (1H and 13C) into the dipolar and contact contributions. The positive sign of the 13C contact shift is in accord with the usual spin alignment of the free europium ion relative to the external field together with a negative coupling constant. The opposite sign of the 1H contact shift is explained by a polarization mechanism. The anomalous temperature dependence of the 1H contact shift is connected with the strong second order paramagnetism of the europium ion.

Paramagnetic Susceptibilities of Some DPPH Derivatives

Abstract The static magnetic susceptibilities of poly crystalline samples of 1,1-bis(p-chlorophenyl)-2-picrylhydrazyl (Cl-DPPH), 1,1-bis(p-bromophenyl)-2-picrylhydrazyl (Br-DPPH), and 1,1-bis (p-methoxyphenyl)-2-picrylhydrazyl (CH3O-DPPH) were measured in the temperature range from 10°K to 300°K. These three substances showed strong paramagnetism comparable to that of DPPH, having relatively weak interaction energies between their unpaired electrons. Of these, the paramagnetic susceptibility of CH3O-DPPH was analysed on the basis of the singlet-triplet model with the energy separation of 2J/k=33.8°K.

Pair-Breaking Mechanisms in Superconductors

A review is given of the theoretical and experimental situation concerning the problem of superconductivity in the presence of pair-breaking perturbations. The problem was first considered by Abrikosov and Gorkov, who advanced a theory which explained the results of the experiments by Matthias and co-workers on the lowering of Tc of superconductors containing small concentrations of magnetic impurities. The theory predicted further that the presence of magnetic scattering centers severely distorts the excitation spectrum of a superconductor and that for sufficiently large spin concentrations the energy gap disappears from the spectrum, even at T=0°K. It has since been found that the AG theory can be extended to treat other pair-breaking situations which lead to second-order superconducting-normal phase transitions. Examples of these are the vortex state, the surface sheath state, the proximity effect, small superconductors in large magnetic fields, superconductivity in the presence of high currents, and superconductivity in the presence of strong Pauli paramagnetism. In the dirty limit (where the mean free path is much smaller than the zero-temperature coherence length) the different pair-breaking regimes are equivalent in that their behavior is specified by a unified single parameter theory. In transforming from one pair-breaking regime to another, one needs only to change the pair-breaking parameter. Experimental results from the different depairing regimes are presented and compared with the predictions of the unified theory.

A Cobalt Complex Catalyst for the Linear Dimerization of Butadiene

Abstract In the linear dimerization of butadiene, the mixing order of butadiene and catalyst components, cobalt acetylacetonate and triethylaluminum affects the activity of the catalyst. When cobalt acetylacetonate and triethylaluminum react in the presence of butadiene, the solution possesses marked catalytic activity. In the infrared spectrum of this system, the intensity of the absorption peaks of the CH-(1008 cm−1) and CH2- (908 cm−1) wagging vibrations of butadiene decrease significantly as compared with the case when butadiene is added last. In both cases, the absorption of Co–O (466 cm−1) disappered and that of Al–O (490 cm−1) was found. These results indicate that triethylaluminum reduces cobalt acetylacetonate and coordinates butadiene to cobalt. When butadiene is absent, triethylaluminum and cobalt acetylacetonate react to form a complex to which butadiene coordinate scarcely at all afterwards. The former solution shows a weak paramagnetism (μeff=1.4), while the latter shows a strong paramagnetism (μeff=4.0), From these results, the catalyst of the reaction is considered to be a diamagnetic complex of cobalt coordinated by butadiene.

Ferromagnetism of an Electron Gas

Magnetism, especially ferromagnetism, of an electron gas is studied on the basis of the Bohm-Pines collective description of electron interactions. Exchange interactions are derived from the screened Coulomb interaction, the interaction obtained from the second-order perturbation of the screened Coulomb interaction, and the weak interaction coming from the interaction between plasma and individual electrons. We assume effective mass for the electron mass. The total energy of the electron gas in the ferromagnetic state is compared with that in the non-ferromagnetic state, and the conditions of ferromagnetism for the electron gas are discussed. The one-electron approximation being adopted, the effective number of magnetic carriers in the electron gas is expressed as a function of temperature and magnetic field. Using the Weiss approximation, we express the spontaneous magnetization at an arbitrary temperature in terms of this effective number and the molecular field obtained from the proper average of the exchange interactions. At low temperatures, the spin-wave approximation is adopted. The Curie temperature, the paramagnetic susceptrbility above the Curie point, and the temperature variation of spontaneous magnetization at low temperatures are determined as functions of the effective mass and the electron mean distance. Using the effective masses determined so as to explain the experimental values of the electronic heats, we make a comparison with experimental values for Ni, Co and Fe. It shows satisfactory agreement in the case of positive hole gas. The strong paramagnetism of γFe, Pd and Pt are also satisfactorily explained, and the inverse of their susceptibilities is well expressed as the sum of a constant term and the term proportional to T 2 at comparatively lower temperatures.

Zum magnetischen verhalten von aluminium und aluminium-mischkristallen

Measurements of susceptibility of aluminium between 67°K and 293°K showed a behaviour which is to be expected for the paramagnetism due to the spins of the conduction electrons. Extrapolation of χ to T = 0 yields a value for the density of states N( E 0) at the Fermi surface which agrees surprisingly well with the theoretical calculations of Matyas and with the value that can be derived from the measured specific heat of the electrons. On the other hand χ decreases with increasing temperature more rapidly than one would expect according to the N( E) function of Matyas. The changes of χ by addition of other metals as measured by Auer are employed in the discussion. Manganese in dilute solid solution in Al gives rise to a strong additional paramagnetism which does not show the temperature dependence that is generally observed at low Mn concentrations.