On the reorientation transition of ultra-thin Ni/Cu(001) films

The reorientation transition of the magnetization of ferromagnetic films is studied on a microscopic basis within a Heisenberg spin model. Using a modified mean field formulation it is possible to calculate properties of magnetic thin films with non-integer thicknesses. This is especially important for the reorientation transition in Ni/Cu(001), as there the magnetic properties are a sensitive function of the film thickness. Detailed phase diagrams in the thickness-temperature plane are calculated using experimental parameters and are compared with experimental measurements by Baberschke and Farle (J. Appl. Phys. 81, 5038 (1997)).Comment: 7 pages(LaTeX2e) with one figure(eps), accepted for publication in JMMM. See also http://www.thp.Uni-Duisburg.DE/Publikationen/Publist_Us_R.htm

Anisotropy of ultra-thin ferromagnetic films and the spin reorientation transition

The influence of uniaxial anisotropy and the dipole interaction on the direction of the magnetization of ultra-thin ferromagnetic films in the ground-state is studied. The ground-state energy can be expressed in terms of anisotropy constants which are calculated in detail as function of the system parameters and the film thickness. In particular non-collinear spin arrangements are taken into account. Conditions for the appearance of a spin reorientation transition are given and analytic results for the width of the canted phase and its shift in applied magnetic fields associated with this transition are derived.Comment: 6 pages, RevTeX

Methods of collecting country checks

Thesis (BA)--University of Illinois, 1905TypescriptIncludes bibliographical reference

Theory of the Spin Reorientation Transition of Ultra-Thin Ferromagnetic Films

The reorientation transition of the magnetization of ferromagnetic films is studied on a microscopic basis within Heisenberg spin models. Analytic expressions for the temperature dependent anisotropy are derived from which it is seen that the reduced magnetization in the film surface at finite temperatures plays a crucial role for this transition. Detailed phase diagrams in the temperature-thickness plane are calculated.Comment: 6 pages(LaTeX2e), one figure(eps), accepted for publication in JMM

2,5-Bis[4-(dimethyl­amino)­phen­yl]-3,6-dimethyl­pyrazine

The title compound, C22H26N4, was prepared from p-dimethyl­amino­propiophenone in six steps. The mol­ecule has no crystallographic symmetry. The dihedral angles between the pyrazine ring and the phenyl rings are 35.81 (6) and 37.11 (8)°. The dimethyl­amino groups are essentially planar (sum of the bond angles at N = 359.3 and 359.9°) and nearly coplanar with the adjacent aromatic ring [dihedral angles = 5.54 (11) and 7.40 (3)°]. This effect and the short aniline C—N bonds can be rationalised in terms of charge transfer from the amino groups to the central pyrazine ring

4-Diethyl­amino-3,5-diisopropyl­benzalde­hyde

The title benzaldehyde, C17H27NO, was prepared via lithia­tion of bromoaniline and reaction with DMF. In the crystal, the molecule adopts a C2-symmetrical conformation; nevertheless, two modes of disorder are present: the orientation of the aldehyde group (occupancy ratio 0.5:0.5) and of symmetry-equivalent ethyl groups [occupancy ratio 0.595 (7):0.405 (7)]. The phenyl­ene ring and the carbonyl group are essentially coplanar [C—C—C—O torsion angle = −179.0 (4)°] but the dihedral angle between the mean planes of the phenyl­ene ring and the amino group = 67.5 (2)°. This and the long [1.414 (3) Å] aniline C—N bond indicate electronic decoupling between the carbonyl and amino groups. The angle sum of 359.9 (2)° around the N atom results from steric compression-induced rehybridization

2,7-Bis(2-nitro­phen­yl)-9-octyl-9H-carbazole

The title compound, C32H31N3O4, was obtained in a Suzuki coupling of carbazole diboronic acid and bromo­nitro­benzene. In the crystal, the mol­ecule adopts a non-symmetric conformation. The carbazole ring system is approximately planar [maximum deviation from the least-squares plane = 0.039 (2) Å]. The planes of the carbazole unit and the benzene rings subtend dihedral angles of 48.42 (7) and 41.81 (6)°. The dihedral angles between the planes of the nitro­phenyl rings and the nitro groups are 44.34 (19) and 61.64 (15)°. The crystal is built from two strands of parallel mol­ecules with inter­digitated octyl chains. These strands are symmetry related by a twofold screw axis

Reorientation transition of ultrathin ferromagnetic films

We demonstrate that the reorientation transition from out-of-plane to in-plane magnetization with decreasing temperature as observed experimentally in Ni-films on Cu(001) can be explained on a microscopic basis. Using a combination of mean field theory and perturbation theory, we derive an analytic expression for the temperature dependent anisotropy. The reduced magnetization in the film surface at finite temperatures plays a crucial role for this transition as with increasing temperature the influence of the uniaxial anisotropies is reduced at the surface and is enhanced inside the film.Comment: 4 pages(RevTeX), 3 figures (EPS