Magneto-optical method

Search for the missing halogen, eka-iodine, was actively pursued for many years. One of the most widely publicized claims for its discovery was that of F. Allison who developed a magneto-optical method by which he believed he had identified the element. He named it alabamine (25). The claim was not subsequently verified, and the element was actually found only after use of the cyclotron began. 

Fig. 8.22. The vanishing radiative width in the Ba spectrum. Experimental data are shown which correspond to oscillator strength measurements below the ionisation threshold by the magneto-optical method described in chapter 4, which also gives an overview of the Ba spectrum including the broad 5d8p perturber responsible for the vanishing radiative width. The inset shows a comparison between measured values (squares) and an MQDT extrapolation (triangles) on a logarithmic scale (see also fig. 4.3 - after J.-P. Connerade et al. [136]).

Magneto-optical properties of the compounds CrTe and Cr3Te4 were investigated by Comstock and Lissberger (1970) and Atkinson (1977), respectively. In both cases the perpendicular remanence ratio was determined by magneto-optical methods and found to be rather low. This is due to an easy magnetization direction parallel to the plane of the thin films on which the measurements were performed. Specific Faraday rotation and Kerr rotation were reported to be low compared to MnBi. 

A magnetometer commonly measure samples in an integrative manner, integrating the magnetic moment over the entire volume in contrast to, e.g., magneto-optical methods which give more local information about the specimen. The method is in general noninvasive. 

Moseley demonstrated clearly that there was a gap and a missed element between polonium and radon. A discovery of this element, number 85, was announced in 1931 by a group of scientists at Alabama Polytechnic Institute. They had dissolved mon-azite in aqua regia and claimed, after examination with a magneto-optic method [52.12], that the sought element was present in the solution at a concentration corresponding to 0.0000001% of the monazite weight The element was named alabami-um Ab after Alabama. The claim could not be verified and the discovery was not approved. 

F. Alison, Magneto-Optic Method of Analysis as a New Research Tool, Ind. Eng. Chem. Anal. Ed. 1932, 4, 9—12... 

In these geometries, the sample cell is usually observed in the transmitted light with crossed polarizers inserted in 45° orientation to the director tilt plane. While the ordinary polarized light in the birefringent medium always experiences the ordinary index of refraction and is unaffected by the deformation, the optical path of the extraordinary wave is sensitive to the director tilt. Both waves are brought to interference at the analyser and the optical interference can be related in a direct way to the director deflection. Saupe first used this magneto-optical method with splay geometry to determine the splay and bend constants of p-azoxyanisol (PAA) [13]. 

Like in the magneto-optical method, optical detection may be applied in the electrically driven case as well. As an alternative, the cell capacitance C is a convenient measure of the transition threshold and the tilt deformation of the director field. The capac-itanee versus voltage curves can be used to determine the dielectric and elastic constants and the surface tilt angles [ 19]. A", is given by the critical field and 33 is obtained from the slope of the C U) curve. In the... 

The experiments can be subdivided into, for example, magneto-optical methods [22,119,... 

A magneto-optical method to measure the particle size using the Faraday effect has been developed in samples with the same Fe/Si molar ratio but different diameters of the magnetic nanoparticles. The increase of Faraday rotation with the mean diameter of the y-Fe203particles was associated with surface effects [43]. 

Rosa, G. et al. (2005) Surface effects in magnetic nanoparticles measured by means of a magneto-optical method. /. Appl. Phys., 97 (6), 064314-064314-5. 

An example of this process of data analysis is provided by the work of Yubero et al. (2000), who studied the structure of iron oxide thin films prepared at room temperature by ion beam induced chemical vapour deposition. Such films find important applications because of their optical, magnetic, or magneto-optical properties. They were produced by bombardment of a substrate with Oj or Oj + Ar+ mixtures, and Figure 4.15 shows RBS spectra of two iron oxide thin films prepared on a Si substrate by each of these bombardment methods. 

In conclusion, we have presented a reliable method for selective production and detection of high-order atomic polarization moments based on the nonlinear magneto-optical effects with frequency modulated light. This method can be used for the selective control of higher order atomic coherences in multilevel systems exploiting large Kerr nonlinearities for the construction of all-optical quantum phase gates. 

For nonlinear (magneto-) optical properties, calculations of an accuracy close to that of modern gas phase experiments require - similar to what has also been found for other properties like structures [79, 109], reaction enthalpies [79, 110, 111], vibrational frequencies [112, 113], NMR chemical shifts [114], etc. - at least an approximate inclusion of connected triple excitations in the wavefunction. This has been known for years now from calculations of static hyperpolarizabilities with the CCSD(T) approximation [9-13]. CCSD(T) accounts rather efficiently for connected triples through a perturbative correction on top of CCSD. For the reasons pointed out in Section 2.1 CCSD(T) is, as a two-step approach, not suitable for the calculation of frequency-dependent properties. Therefore, the CC3 model has been proposed [56, 58] as an alternative to CCSD(T) especially designed for use in connection with response theory. CC3 is an approximation to CCSDT - alike CCSDT-la and related methods - where the triples equations are truncated such that the scaling of the computational efforts with system size is reduced to as for CCSD(T),... 

The magneto-optical spectroscopy technique has certain advantages over FTIR (1) It can penetrate layers such as active layers as well as layers associated with some heterostructures, (2) It does not require contacts, (3) donors and acceptors can be Identified simultaneously permitting an estimate of sample compensation, and (4) since It samples a very thin layer of material it can be used In profiling layers. These two techniques provide methods for Identifying very shallow levels In semiconductors. 

---