Magnetic Coupling Properties Research Articles

Electric and magnetic coupling properties: crystals and polycrystals

Se revisa el estado del arte de las propiedades de acoplamiento asociadas a estimulos y respuestas de naturaleza electrica y magnetica en ceramicas. Se presentan las familias de materiales sobre las cuales se realizan en la actualidad las investigaciones mas significativas en relacion con los efectos considerados y se senalan algunos grupos de trabajo representativos. Se expone un resumen formal de la cristalofisica de las propiedades de acoplamiento. Las herramientas analiticas utilizadas son las simetrias ordinaria y complementaria de estructura y propiedades, ademas de los tensores polares y axiales. Se plantea la llamada representacion superficial de las propiedades, tanto para monocristales como para ceramicas policristalinas. Se introducen los metodos del Analisis de Texturas y el calculo de propiedades de acoplamiento efectivas (promedios) con empleo de las funciones de distribucion de orientaciones. Se muestran ejemplos practicos de las tecnicas expuestas.

Amorphous Fe-Si and Fe-Ge nanostructures quantitatively analyzed by x-ray-photoelectron spectroscopy

The subject of this paper is an x-ray-photoelectron spectroscopy investigation of amorphous Fe-Si and Fe-Ge nanostructures that have attracted interest because of their magnetic coupling properties. To this end we deposit Fe onto clean, amorphous Si and Ge substrates at room temperature and at 40 K, respectively. We take spectra of the $\mathrm{Fe}3p,$ $\mathrm{Fe}2p,$ and $\mathrm{Si}2p$ core levels to determine possible chemical shifts. The results indicate a charge transfer from the Fe to the Si and Ge atoms at room temperature as well as at 40 K. Additionally, we record wide range spectra of the $\mathrm{Si}KLL,$ $\mathrm{Ge}LMM,$ and the $\mathrm{Fe}2p$ peaks as well as spectra of Fe-Si, and Fe-Ge compounds, respectively. Analyzing the inelastic background of the peaks we quantitatively determine the nanostructure of the deposits. We can exclude the formation of sharp interfaces. Instead, we find evidence for the formation of an Fe-Si or Fe-Ge interface compound with a homogeneous composition. For magnetically investigated low-temperature prepared Fe/Si/Fe trilayers we show that the spacer layer is a pure semiconductor with a thickness that is reduced compared to the nominal value.

The Magnetic Coupling, Optical and Magneto-Optical Properties of Oscillation Observed in Sputtered Co–Al/Cu Multilayers

We have studied the optical and magneto-Optical properties, and the behavior of interlayer coupling and magnetoresistance in sputtered [Co90Al10(1.6 nm)/Cu]30 multilayers. It is found that for Co–Al/Cu multilayers, the magnetoresistance ratio ΔR/R, the in-plane saturation field Hs and coercive force Hc oscillate with a period of about 0.9 nm, as a function of the Cu layer thickness. It is significant to find that the magneto-Optical polar Kerr rotation θK, and particularly the effective dielectric constant ε oscillate in a period of about 0.9 nm. This result can be attributed to the oscillations of the optical constants in Cu spacer layers, induced by the oscillatory interlayer coupling or quantum well effect. Numerical calculations show that the oscillations of the effective optical constants play an important role in the magneto-Optical Kerr effect oscillations.

Magnetic Coupling in the Ni-Pd Alloy System

The magnetic coupling properties of the Ni-Pd alloy system are considered in terms of a molecular-field solution based on a Heisenberg type of interaction for spin \textonehalf{}. The unpaired electrons in Ni are assumed to be part of a band of mainly ${t}_{2g}$ character in which the totality of interactions leads to an interatomic ferromagnetic coupling. The unpaired electrons in pure Pd are assumed to be part of a narrow, weakly interacting band with more nearly ${e}_{g}$ symmetry. In the alloy, the Pd band structure becomes progressively more like that of Ni. The magnetic energy is then calculated in terms of the probability of finding unpaired electrons in the overlapping orbitals of the Ni and Pd atoms. The probability is determined from the average moment curve on the assumption of $3{d}^{9}$ and $3{d}^{10}$ states only. A fit to the data on the Curie temperature and average magnetic moment then gives the following relative values for the exchange constants (molecular-field coefficients); $A$ for Ni-Ni, $\ensuremath{\alpha}A$ for Ni-Pd, and ${\ensuremath{\alpha}}^{2}A$ for Pd-Pd, with $\ensuremath{\alpha}\ensuremath{\cong}0.8$.