Junkichi Itoh

Nuclear Magnetic Resonance In Co Alloys

NMR satellite lines were observed at frequencies lower than main line in Co alloys with dilute impurities, It is concluded that these satellites are due to the Co nuclei located at the nearest neighbor sites of the impurities and that the changes of magnetic moments are well localizes around the impurities. An equation is derived which can represent the frequencies of satellites. Some physical interpretations are given for the equation.

Nuclear Magnetic Resonance Experiments on Ammonium Halides, II Halogen Nuclear Magnetic Resonance

The chemical shift, spin-lattice relaxation time, and intensity of nuclear magnetic resonance line were measured for ammonium chloride, bromide and iodide in various phases. It was found that the reorientational motion of ammonium ion is the origin of time dependent interaction necessary to relax the nuclear spin orientation. The deformation of the halogen ion core, arising from the interaction with alkali ions, is discussed in connection with the chemical shift and spin-lattice relaxation time. In ordered phase, T 1 in the chloride became much longer than that in phase II, while in the bromide electric quadrupole splitting of NMR line appeared, and the ordering parameter was estimated. From the result of the intensity measurements, the effect of crystal imperfection upon NMR is discussed.

Nuclear Magnetic Resonance Experiment on Solid Hexamethyldisilane

Proton magnetic resonance of solid hexamethyldisilane was studied. Line width and spin-lattice relaxation time were measured in temperature range from liquid air to room temperature. By analysing these quantities following results were obtained: Even at liquid air temperature, each CH 3 group reorientates about its three-fold symmetry axis so rapidly as to narrow the dipolar width due to three proton interactions within itself (activation energy 2.6 kcal/mole). Then at about -120°C, reorientation of CH 3 -groups about the axis joining two silicon atoms becomes rapid enough to narrow the width further (activation energy 5.7 kcal/mole). Spin-lattice relaxation time varies qualitatively in accordance with the above considered reorientational motions. At -51.3°C, this crystal changes its structure and at the same time rapid reorientational motion of the molecular axis is excited, resulting discontinuous decrease in the line width and discontinuous increase in the spin-lattice relaxation time. Above the transi...

Paramagnetic Resonance Spectrum of Mn++ in NaCl Single Crystal

The paramagnetic resonance spectrum of Mn ++ ions contained in NaCl single crystal with concentrations of 1∼3×10 -4 in mole fraction has been investigated. From the analysis of the spectrum the existence of Mn ++ –Na + vacancy complex, in which a Na + vacancy is at one of the nearest neighbor positions with respect to the Mn ++ ion, has been verified at room temperature in crystals quenched from high temperatures. However, this state of Mn ++ ion is unstable at room temperature, and such complexes diffuse through the lattice to form aggregates of Mn ++ ions. The ground level splitting parameters of a Mn ++ ion accompanying a Na + vacancy at one of its nearest neighbor positions have been obtained as follows: D =137.9±1 gauss, E =51.4±0.4 gauss, where D and E represent the parameters in the spin Hamiltonian, D [ S z 2 -1/3· S ( S +1)]+ E ( S z 2 - S y 2 ), in which z axis is in the direction of Mn ++ –Na + vacancy and y axis along the cubic axis perpendicular to it.

Nuclear Magnetic Resonance in α- and β-Manganese Metals

Nuclear magnetic resonance studies on Mn 55 in α- and β-Mn metals have been made by both the steady and the pulse methods. Nuclear spin-lattice relaxation time T 1 and spin-spin relaxation time T 2 were measured by the pulse method in the temperature range of 1.5°K to 77°K. The measured value of T 1 T of β-Mn keeps a constant value of 7 m sec °K through the temperature range measured. Using both the T 1 T value and the Knight shift, the origin of the effective magnetic field acting on a nucleus in a Mn metal was concerned. T 2 of 0.1 m sec. was observed to be temperature independent. Several nuclear spin-lattice relaxation mechanisms together with the origin of the effective magnetic field in the Mn metal are discussed. T 1 due to the dipole, quadrupole, and orbital interactions is calculated using free electron approximation in which the electronic wave function includes partly p - or d -character. It is shown that the orbital interaction is more effective than those due to the dipole or quadrupole inter...

NMR Study in PdCo and PdNiCo Alloys

NMR of Co 59 has been performed in ferromagnetic PdCo alloys. The internal field changes from -215 kOe in pure Co metal to 230±5 kOe in alloys of Co diluted in Pd. The results are consistent with the previous measurements by nuclear polarization and Mossbauer effect experiments. The line width is very broad in alloys with low Co concentration. Even in 0.5% Co alloy, the width still has the value of 50 MHz. T 2 shows rapid decrease with decreasing Co concentration. The experiment has also been performed on Co 59 in ferromagnetic Pd x Ni 1- x Co system. The results are quite similar to those in PdCo alloys.

Nuclear Magnetic Resonance Studies of Ammonium Halides. I. Proton Magnetic Resonance in Single Crystals of Ammonium Chloride and Ammonium Bromide

Line shapes of proton magnetic resonance absorption in single crystals of ammonium chloride and bromide were measured in temperature range from 90°K to room temperature. At liquid air temperature, broad lines with structures corresponding to rigid configuration of ammonium ions were observed for both crystals. These structures were analysed by solving the nuclear magnetic energy levels of ammonium ion containing four protons and one nitrogen nucleus, and also by estimating the width of each component line. Theoretical line shapes coincide well with experimental ones in the chloride, but the agreement is worse in the bromide. Some possible origins for the disagreement in the latter case are discussed. Line width at higher temperatures narrowed by rapid rotation of ammonium ions was measured for various orientations of the crystal. A slightly discontinuous change of the second moments of the line was observed at the order-disorder transition point in the bromide.

Nuclear Magnetic Resonance and Relaxation of 159Tb in Ferromagnetic Terbium Metal

Nuclear magnetic resonance and relaxation of 159 Tb in ferromagnetic Tb metal were investigated by spin echo technique at liquid helium temperatures. The nuclear magnetic resonance spectrum consists of three equally separated lines in the frequency range from 2.4 GHz to 3.9 GHz. The center line frequency which corresponds to the Zeeman frequency is 3120 MHz and the frequency difference of the adjacent lines which represents the electric quadrupole effect is 673.5 MHz. It is found that spin-lattice relaxation is produced mainly by the process in which the nuclear energy relaxes to the kinetic energy of the conduction electrons via spin waves (Wegers mechanism), as in the case of Dy nuclei in ferromagnetic Dy metal, and the spin-spin relaxation time is determined by the spin-lattice relaxation and the I · I coupling.

Nuclear Magnetic Resonance Experiment on the Single Crystals of K2HgCl4·H2O and K2SnCl4·H2O. II, The resonance absorption due to four proton system and the revised determination of their crystal structures

The energy levels and the transition probabilities are calculated for four proton interaction. The result of calculation is applied to the case of the single crystals of K 2 HgCl 4 ·H 2 O and K 2 SnCl 4 ·H 2 O. Ten absorption lines are expected from the theoretical calculation, of which each five form a group. Since in general cases the separations between the lines belonging to one of these groups are small compared to the separation between these groups as a whole, the expected resonance figure roughly coincides with the case of two proton resonance. But the shapes of resonance peaks have further fine structures. The observed fine structures were analysed by the theoretical consideration, and it is shown that the agreement between the theory and the experiment is satisfactory, if we take the distance of main protons to be 1.607 A and the distance between the proton-proton lines for adjacent water molecules which are parallel with each other to be 3.60 A in the case of Hg-salt and 1.62 A and 3.90 A respe...

The Hyperfine Interactions of Terbium, Dysprosium and Erbium in Magnetically Ordered Heavy Rare Earth Alloys

NMR spectra of Tb 159 , Dy 163 and Er 167 in various heavy rare earth alloys which are all in magnetically ordered states were investigated at liquid helium temperature, and the values of magnetic dipole and electric quadrupole hyperfine interactions were determined. In these heavy rare earth alloys, the main contribution to the hyperfine interactions arises from the unfilled 4f electrons of the parent ion. But there exist some other minor contributions; the electric quadrupole interaction arising from the lattice and conduction electron charges and the internal field produced by the polarization of the conduction electrons, which are discussed by analysing our experimental results.