Spin-flip Scatterings Research Articles

Spin-Flip Scattering and the Dynamics of the Superconducting Order Parameter

Pair-field susceptibilities of Al films doped with the magnetic impurity Er have been measured. The spin-flip scattering time determined from studies above T/sub c/ is consistent with the results of electron spin resonance measurements. Below T/sub c/ the transverse mode of the order parameter propagates only when there is a gap in the excitation spectrum.

Quasispin model of itinerant magnetism: High-temperature theory

The high-temperature properties of itinerant magnetic systems are examined by using the coherent-potential approximation. We assume a local moment on each atom so that at elevated temperatures there is a number of reversed spins. The coherent potential is solved, and from that the moment on each atom is determined self-consistently. It is found that when the condition for ferromagnetic ordering is satisfied, the local moments persist even above the critical temperature. Conversely, if local moments do not exist at high temperatures, the system can at most condense into a spin-density-wave state. Furthermore, spin-flip scatterings of the conduction electrons from the local moments give rise to additional correlation not treated in the coherent-potential approximation. This correlation energy is an important part of the coupling energy of the local moments. The relations between our work and the theories of Friedel, Hubbard, and others are discussed.

Spin-Flip Scattering from Free Holes

Spin-Flip Scattering from Free Holes

Spin-Flip Scattering of Pions by Nuclei

Spin-Flip Scattering of Pions by Nuclei

Spin-Flip Scattering Cross Section for Conduction Electrons of Foreign Atoms in Lithium and Sodium. I

We have measured the spin-flip scattering cross section for conduction electrons of impurities in metallic sodium and impurities in metallic lithium. The cross sections are deduced from the measurements of the dependence on impurity concentration of the linewidth of the conduction-electron spin resonance. Since the apparatus was an $X$-band superheterodyne spectrometer and the samples were small particles of about 10-\ensuremath{\mu} diam, the Dyson theory must be applied to relate measured linewidth to relaxation time and thus to cross section. A simple theoretical analysis is applied which involves the numerical solution of the non-spin-flip scattering by a screened Coulomb potential whose screening length is adjusted so that the $s$, $p$, and $d$ scattering phase shifts satisfy the Friedel sum rule. We then orthogonalize these solutions to the core states of the impurity atom. Using these orthogonalized wave functions and assuming the spin-flip scattering results from a coupling of the electron spin to its orbital motion in the vicinity of the nucleus of the impurity, we use perturbation theory to compute a spin-flip scattering cross sections which has no adjustable parameters. The result accounts well for the magnitudes and trends as one moves down and across the periodic table for those impurities whose valence differs from that of the host by 0, 1, or 2 units. The theory does not account for the existence or position of a maximum as one moves across the periodic table.

Spin-Flip Scattering Cross Section for Conduction Electrons of Foreign Atoms in Lithium and Sodium. II

We calculate spin-flip scattering cross sections for conduction electrons of a number of impurities in metallic lithium and sodium, in order to improve on the results reported in our earlier paper. The method uses the numerical integration of a potential which is derived from the Herman-Skillman atomic potential near the impurity, and is flat beyond a suitably chosen radius. Screening is included by requiring that the Friedel sum rule be satisfied. No parameters of the theory are adjusted to fit experimental data. The agreement for resistivity, Knight shift, and spin-flip scattering cross section is good for valence differences between impurity and host of 1 or 2. The theory gives a maximum in the cross section as the valence increases, but places the maximum at a valence difference of 4 instead of the experimentally observed value of more nearly 2.

Spin-Flip Scattering of Conduction Electrons from Impurities in Molten Sodium

Spin-Flip Scattering of Conduction Electrons from Impurities in Molten Sodium

Spin Flip Scattering of Conduction Electrons from Impurities

Recent experiments on the spin flip scattering of conduction electrons by nonmagnetic impurities in certain metals have established that the scattering cross section does not increase monotonically with the charge (valence) of the impurity. It is suggested here that this may be due to a “resonant scattering” of the electron by the impurity potential (the term ‘resonant’ being used in a certain sense) and a subsequent spin flip scattering by the spin orbit impurity potential. This interplay of the two potentials is best illustrated by amploying a separable potential model. An over simplified 3 parameter model is constructed out of this which is found to be in qualitative agreement with experiment.

Spin-Flip Scattering of Conduction Electrons from Impurities

Spin-Flip Scattering of Conduction Electrons from Impurities

The Spin-Flip Scattering of High Energy Protons by Light Nuclei

The spin-flip inelastic scattering of high energy protons is investigated for the 15.1 Mev excitation of C12 ancl the 9.2 Mev excitation of N14. The electromagnetic interaction is found to be far too weak to account for the observed cross sections. The spin-flip cross sections clue to the (rr1 ·<r2) (-r1 part of the nuclear interaction are calculated by means of the impulse approximation. In the case of C12 the cross section can l1e calculated without referring to any special nuclear model from theft-value of the fl-clccay of B12 or N 12 to the ground state of C12. The result agrees very well with the experimental cross section showing the validity of the assumptions involved in the calculation. It is also shown that the spin-flip scattering is the only process which shows the angular distribution with maximum at Oo leaving the residual nucleus in a discrete low-lying excited state. The nuclear matrix element of the transition estimated conversely from the observed cross section may be used as a datum: for the relevant nuclear states. In particular the separate contributions of the spin and the orbital angular momenta to the M1 r-transition between the relevant states can be estimated and are found to be of the ratio 1 to 0.3 both for C12 and NI4. Discussions arc given on the approximations used in the calculations as well as on the nuclear states relevant to the excitations.