Magnetic Synchrotron Research Articles

Structural and magnetic behavior of the S=2 layered ferromagnet CsMnF4 under hydrostatic pressure.

Pressure-induced transformations in the structural and magnetic properties of ${\mathrm{CsMnF}}_{4}$ are reported. This behavior is analyzed in the framework of magnetostructural correlations within the layered perovskite A${\mathrm{MnF}}_{4}$ (A=Cs,Rb,K) series by using magnetic susceptibility and synchrotron x-ray powder-diffraction techniques as a function of temperature and hydrostatic pressure.

A high-resolution NMR and synchrotron x-ray powder diffraction study of zeolite ZSM-11

High-resolution nuclear magnetic resonance (NMR) spectra and synchrotron x-ray powder diffraction data have been obtained from a well-crystallized highly dealuminated sample of the zeolite ZSM-11. The Rietveld profile technique has been applied to the synchrotron data to give the first detailed refinement of the idealized structure derived ten years ago by distance least-squares modeling methods [G. T. Kokotailo, P. Chu, S. L. Lawton, and W. M. Meier, Nature 275, 119 (1978)], which involves 54 variable atomic positional parameters. The structure is tetragonal (a = 20.065 Å, c = 13.408 Å at 25 °C) and consistent with the previously reported tetragonal space group I \overline 4 m2, but the NMR spectra indicate local deviations from this symmetry that disappear at 100 °C.

Motion of relativistic charges in an increasing magnetic field

We discuss the motion of a relativistic test charge moving toward a strong increasing magnetic field when the dominant forces controlling the particle's motion are the magnetic mirroring effect and synchrotron radiation. Equations of motion are established and greatly simplified when the magnetic field has a power-law dependence on distance. The final fate of the particle is either being bounced by the magnetic mirror or gyrating in the lowest Landau orbit while coasting indefinitely with finite forward velocity. Which final fate the test particle ends up in is qualitatively determined by the mirror to radiation ratio |$\zeta\equiv(3m^3c^6/4e^4B^3)(\hat B \cdot \nabla B)$|⁠. The distinct regions in the phase space occupied by these two classes of solutions are sought and various astrophysical applications discussed.

On the origin of the infrared and X-ray continua of active galactic nuclei

The continuum spectra of radio-quiet active galactic nuclei, which are steeper in the near-IR and flatter in the X-ray regime, can be produced in a synchrotron self-Compton model with a broken power law electron distribution that is flat at low, and steep at large, Lorentz factor values. While the steeper part generates the IR spectrum via synchrotron process, both parts together produce the flatter X-ray spectrum via Compton scattering. The intersection of the two spectra corresponds to equipartition between the magnetic field and synchrotron photon energy densities, giving approximately the same luminosities in the synchrotron and Compton components. The photon spectra are self-consistently computed here, taking the effects of cooling, e(+)e(-) pair production, and higher order Compton scattering into account.

Magnetic fields, bremsstrahlung and synchrotron emission in the flare of 24 October 1969

An impulsive flare October 24, 1969 produced two bursts with virtually identical time profiles of 8800 MHz emission and X-rays above 48 keV. The two spikes of hard X-rays correspond in time to the times of sharp brightening and expansion in the Hα flare. The first burst was not observed at frequencies below 3000 MHz. This cut off is ascribed to plasma cutoff above the low-lying flare.A model of the flare based on Hα observations at Big Bear shows that the density of electrons with energy above 10 keV is 5 × 107 if the field density is 1011. The observed radio flux would be produced by this electron distribution with the observed field of 200 G. The Hα emission accompanying the hard electron acceleration is presumed due to excitation of the field atoms by the hard electrons.