Physics Commons^™

Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek

Christian Binek Publications

Discontinuous magnetic multilayers [Co80Fe20(t)/Al2O3(3nm)]10 with t = 0.9 and 1.0nm are studied by SQUID magnetometry and ac susceptibility. Owing to dipolar interaction the superparamagnetic cluster systems undergo collective glass-like freezing upon cooling. While both samples exhibit very similar glass temperatures Tg » 45 K and critical exponents zn » 10 and g » 1.4 as obtained from the temperature dependencies of the relaxation time, t, and the nonlinear susceptibility, c3, dynamical scaling reveals different critical exponents, b(0.9nm) »1.0 and b(1.0nm) » 0.6, respectively.

Effects Of Layer Thickness On Orientation Distribution And Magnetic Properties Of Cocrta/Cr Films, Z. S. Shan, H. Zeng, C. X. Zhu, M. Azarisooreh, K. Honardoost, Yi Liu, David J. Sellmyer

David Sellmyer Publications

No abstract provided.

Magnetic Control Of Convection In Nonconducting Diamagnetic Fluids, J. Huang, D. D. Gray, Boyd F. Edwards

All Physics Faculty Publications

Inhomogeneous magnetic fields exert a body force on electrically nonconducting, diamagnetic fluids. This force can be used to compensate for gravity and to control convection. The field effect on convection is represented by a dimensionless vector parameter R_m=(μ₀αχ₀d³ΔT/ρ₀νD_T)(H⋅∇H)_r=0^ext, which measures the relative strength of the induced magnetic buoyancy force due to the applied field gradient. The vertical component of this parameter competes with the gravitational buoyancy effect and a critical relationship between this component and the Rayleigh number is identified for the onset of convection. …

A Study Of Magnetic Activity Effects On The Thermospheric Winds In The Low Latitude Ionosphere, Ricardo Cruz Davila

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The purpose of this thesis is to examine the effects of magnetic activity on the low latitude F-region thermospheric winds. The F-region (120-1600 km) is a partially ionized medium where O⁺ and O are the major ion and neutral species, respectively. The thermospheric winds at these altitudes are driven primarily by pressure gradient forces resulting from the solar heating during the day and cooling at night. For this study, we use measured Fabry-Perot Interferometer (FPD winds at Arequipa (16.5°S, 71.5°W) and measured FPI and Incoherent Scatter Radar (ISR) winds at Arecibo (18.6°N, 66.8°W).

Previous wind studies at Arequipa and …

Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek

Christian Binek Publications

Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.

Light Diffraction By Field-Induced Non-Periodic Magnetic Domain Structures In Fecl2, Christian Binek

Christian Binek Publications

The magnetic-field-induced mixed phase of the meta magnet FeCl2 gives rise to reduced transmittivity of circularly polarized light. Within the framework of the diffraction theory of thin random magnetic phase gratings and the assumption of field-dependent refractive indices of the antiferromagnetic domains the field dependence of the transmission is perfectly modeled.

Equatorial Electricfields During Magnetically Disturbed Conditions, 1. The Effect Of The Interplanetary Magneticfield, Bela G. Fejer, C. A. Gonzales, D. T. Farley, M. C. Kelley, R. F. Woodman

Bela G. Fejer

Radar measurements of E and F region drift velocities have been used to look for correlations between changes in equatorial electric fields and the interplanetary magnetic field (IMF). The east-west component of the IMF appears to be unimportant, but the north-south component has some effect; rapid reversals from south to north are sometimes correlated with reversals of the equatorial east-west electric field during both daytime and nighttime. This is not always true, however, the IMF may reverse without any apparent effect at the equator. Furthermore, large equatorial field perturbations are sometimes observed when the IMF Bz is large and southward …

Equatorialelectric Fields During Magnetically Disturbed Conditions, 2. Implications Of Simultaneousauroral And Equatorial Measurements, C. A. Gonzales, M. C. Kelley, Bela G. Fejer, J. F. Vickrey, R. F. Woodman

Bela G. Fejer

Simultaneous auroral and equatorial electric field data are used along with magnetic field data to study anomalous electric field patterns during disturbed times. During some substorms, accompanied by ring current activity, the worldwide equatorial zonal electric field component reverses from the normal pattern. This is interpreted as a partial closure of high latitude field aligned currents in the dayside, low latitude ionosphere. These currents flow westward across the dayside. In several cases the zonal equatorial electric field component was nearly identical in form to the zonal auroral component, indicating the close electrical coupling between these regions. Less certain, but equally …