Spin reorientation transition in single-domain

We demonstrate that the interplay of in-plane biaxial and uniaxial anisotropy fields in results in a spin reorientation transition and an anisotropic ac susceptibility which is fully consistent with a simple single-domain model. The uniaxial and biaxial anisotropy constants vary, respectively, as the square and fourth power of the spontaneous magnetization across the whole temperature range up to . The weakening of the anisotropy at the transition may be of technological importance for applications involving thermally assisted magnetization switching.     

Spin reorientation in (RE)2 (TM)14B alloys (RE = rare earth,TM = transition metal)

Spin reorientation in (RE)₂ (TM)₁₄B alloys has been studied by Moessbauer spectroscopy of oriented and powder samples. The competition of the CEF anisotropy for two rare earth elements with opposite Stevens factors has been investigated in the system Er_2-xDy_xFe₁₄B. The competition between the rare earth and transition metal sublattice anisotropy has been examined in the system Nd₂Co₁₄B doped with 1% Fe⁵⁷ and it has been found that spin reorientation occurs at 550±2K.     

Spin reorientation in erbium iron garnet

⁵⁷Fe Mössbauer measurements in the temperature range from 1.5 to 297 K on erbium iron garnet confirm the occurence of a spin reorientation from the [ 100 ] to the [ 111 ] direction. They show that the reorientation takes place gradually between 74 and 95 K. The values and the signs of the quadrupole coupling constants at the octahedral and tetrahedral sites are determined.     

Spin reorientation and structural relaxation of atomic layers: pushing the limits of accuracy

The correlation between an ad-layer-induced spin reorientation transition (SRT) and the ad-layer-induced structural relaxation is investigated by combined in situ surface x-ray diffraction and magneto-optical Kerr-effect experiments on Ni/Fe/Ni(111) layers on W(110). The Fe-induced SRT from in-plane to out-of-plane, and the SRT back to in-plane upon subsequent coverage by Ni, are each accompanied by a small lattice relaxation of at most 0.002 A. Such a small strain variation excludes a magnetoelasticity driven SRT, and we suggest the interface anisotropy as a possible driving force.     

Spin reorientation in silicon-substituted yttrium iron garnet

Mössbauer spectroscopy of a silicon substituted YIG containing 0.3 Si⁴⁺ per formula unit has shown that a spin reorientation, from [111] to [100], occurs between 265 and 80 K. The transitions occur by way of the magnetic space groups $\text{R}\text{3}\text{c}\text{′ →}\text{F}\text{2′}\text{d}\text{′}\text{→}\text{I}\text{4}{}_1\text{ac}\text{′}\text{d}\text{′}$. The broad spin reorientation is mainly a consequence of the persistence of a nonuniform distribution of Fe²⁺ ions over the octahedral sites.     

Formation of textured Ni(200) and Ni(111) films by magnetron sputtering

The effect of the working gas pressure (P ≈ 1.33–0.09 Pa) and the substrate temperature (T_s ≈ 77–550 K) on the texture and the microstructure of nickel films deposited by magnetron sputtering onto SiO₂/Si substrates is studied. Ni(200) films with a transition type of microstructure are shown to form at growth parameters P ≈ 0.13–0.09 Pa and T_s ≈ 300–550 K, which ensure a high migration ability of nickel adatoms on a substrate. This transition type is characterized by a change of the film structure from quasi-homogeneous to quasi-columnar when a film reaches a critical thickness. Ni(111) films with a columnar microstructure and high porosity form at a low migration ability, which takes place at P ≈ 1.33–0.3 Pa or upon cooling a substrate to T_s ≈ 77 K.     

Spin reorientation transition in Fe/CeH2 multilayers probed by soft X-ray resonant magnetic scattering

The magnetic domain configurations of Fe 3d spins in Fe/CeH₂ multilayers were measured by soft X-ray resonant magnetic scattering. The interface region could be probed by setting up X-ray standing waves due to the multilayer periodicity. By resolving first- and second-order magnetic scattering contributions, we show that the latter probe directly the magneto-crystalline anisotropy which is dominated by the Fe interface layers causing a spin reorientation transition when the temperature is lowered. Received: 30 May 2001 / Accepted: 4 July 2001 / Published online: 5 October 2001     

Angular dependent negative magnetoresistance in Si-MOS (111) inversion layers

The negative transverse magnetoresistance effect was observed in n-inversion layers in Si-MOS (111) surfaces at temperatures between 1.5 and 8.3 K. The negative magnetoresistance depends only on the normal component of the magnetic field to the surface and has a saturation value at high fields. The difference between the resistivity at zero field and that at saturation field increases logarithmically with decreasing temperature such as the effect due to the s-d scattering (Kondo effect).     

Spin reorientation and magnon-phonon hybridization in a ferromagnet

A model is presented for the magnetic excitations and magnon-phonon coupling in a localised moment ferromagnet in which spins can reorientate by application of a magnetic field. The model is suitable for those materials which possess a spin wave gap at zero wave vector and therefore the magnon and acoustic phonon branches can intersect. A magnon-phonon coupling linear in both spin and phonon operators is employed which has proved successful for the ferrous salts. The main effect of the applied field is to modify the spin wave gap, and to introduce a critical value for the coupling constant which enables the system to remain stable as the gap goes to zero. Furthermore the wave vector of the anticrossing point decreases as the spin wave gap increases and therefore the value of the sound velocity determined by high resolution inelastic neutron experiments is dependent on the gap.     

Rectification behaviour of molecular layers on Si(111)

Reproducible and strong diode-like behaviour is observed for molecular films of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) on n-type Si(111)- 7×7 surfaces studied by scanning tunnelling microscopy (STM) and spectroscopy (STS) at 77 K. The mechanism behind the rectification is likely to be related to the electron distribution at the molecule-silicon interface. We suggest that the adsorption of the molecular layer profoundly modifies the electronic structure of the Si(111)- 7×7 surface.     

Spin reorientation at the antiferromagnetic NiO(001) surface in response to an adjacent ferromagnet

Polarization dependent x-ray photoemission electron microscopy was used to investigate the spin structure near the surface of an antiferromagnetic NiO(001) single crystal in response to the deposition of a thin ferromagnetic Co film. For the cleaved NiO surface we observe only a subset of bulklike antiferromagnetic domains which is attributed to minimization of dipolar energies. Upon Co deposition a spin reorientation near the NiO interface occurs, with the antiferromagnetic spins rotating in plane, parallel to the spins of the Co layer. Our results demonstrate that the spin configuration in an antiferromagnet near its interface with a ferromagnet may significantly deviate from that in the bulk antiferromagnet.     

Surface quantum oscillations in (110) and (111) n-type silicon inversion layers

Shubnikov-de Haas oscillations have been studied for (110) and (111) n-type silicon inversion layers. The measured cyclotron masses m_c = (0.38 ± 0.03)m₀ and m_c = (0.40 ± 0.03)m₀ for (110) and (111) planes, respectively, are larger than theoretically predicted values. The experimental valley degeneracy factor g_v = 2 ± 0.2 for both orientations is also at variance with self consistent calculations. The electronic g-factor depends on the surface carrier concentration and is enhanced over its bulk value. There was no evidence for the occupation of other subbands.     

Spin polarized energy-resolved photoemission from Ni(111) using synchrotron radiation

We report on the first energy-resolved (retarding field mode) spin polarized photoemission measurement from a Ni(111) single crystal using synchrotron radiation from the ACO storage ring at LURE(ORSAY) It is shown that exchange effects can be detected for electron states well below the Fermi energy and that spin polarized, constant-initial-state spectroscopy of ferromagnets using synchrotron radiation is feasible.     

Passivation of Si (111) surfaces by ordered metal layers

The properties of √3 × √3 ordered gold and silver monolayers on a Si(111) substrate have been investigated by Auger, low energy electron diffraction and photo-emission analysis. It has been found that oxygen adsorption on these surfaces is considerably weaker than on clean Si surfaces. This new result clearly emphasizes the correlation between the oxidation properties of Si atoms and their local environment. A comparison is made with previous results concerning Au-Si amorphous metallic alloys where gold atoms act as a catalyst for the oxidation.     

The epitaxial growth of the chromium bcc (111) layers

Cr/Tb/Cr thin films have been obtained by pulsed laser deposition (PLD) on sapphire substrates. The crystal structure of the films was characterised in-situ by means of reflection high energy electron diffraction (RHEED) and Auger spectroscopy (AS) and ex-situ by X-ray grazing incidence diffraction (GID) and scanning tunnelling microscopy (STM). The deposition of chromium on the Tb(0001) layers at 300 °C was found to lead to the formation of three Cr(110) crystalline domains. Chromium deposited on Tb(0001) initially (first 50 Å) at room temperature and then at 300 °C grew epitaxially in the [111] direction and formed two Cr(111) crystalline domains shifted by 30°. Due to the lower density of the atoms in Cr(111) plane, compared to the Cr(110) and Cr(001) ones, this orientation is interesting for magnetic studies.