Faraday method for magnetic

Electrobalances suitable for thermogravimetry are readily adapted for measurements of magnetic susceptibility [333—336] by the Faraday method, with or without variable temperature [337] and data processing facilities [338]. This approach has been particularly valuable in determinations of the changes in oxidation states which occur during the decompositions of iron, cobalt and chromium oxides and hydroxides [339] and during the formation of ferrites [340]. The method requires higher concentrations of ions than those needed in Mossbauer spectroscopy, but the apparatus, techniques and interpretation of observations are often simpler. 

The magnetic susceptibilities (x) or magnetization (a = x H) for the systems described here were measured by the In-sltu Faraday method described by Mulay [1]. The Mossbauer Spectra were obtained with an Austin Associates spectrometer with a 57co/Rh matrix source (50 mCi) and Nuclear data electronics. In-sltu measurements were made, using a cell similar to that described by Delgass et al. [7]. 

Magnetic Susceptibility Measurements. Magnetic susceptibilities were measured by the Faraday method and were accurate to 2%. Samples, usually as powders, were placed in a cylindrical Teflon boat having an internal volume of 0.30 cc. Measurements were made at 2963, 4357, 5724, 7077, and 8243 G, and at temperatures 77°-295°K. It was possible to correct for ferromagnetic impurities from any field dependent effects. 

Faraday detection as described in Section 3.1., is the traditional method for recording NQR signals. As discussed earlier, Faraday detection sensitivity is limited by the detector s own thermal noise. The desire for improved detection sensitivity has driven the search for non-traditional methods and lower noise Faraday methods of RF magnetic field detection. In this section, several methods that have been applied to NQR signal detection will be discussed. 

Magnetic ORD and CD. Applications of the anomalous dispersion of the Faraday effect for the study of proteins are still limited. For general experimental and theoretical aspects of MORD and MCD and further references see Refs. (42—49). [See below several investigations by these methods on myoglobin, hemoglobin or cytochrome c. ... 

Although for p-azoxyanisole (PAA) a number of measurements in electric fields have been reported (I, 5), only Foex ( ) reported measurements in a high magnetic field. In this paper we report the results of magnetic susceptibility measurements on PAA, which have been obtained by using the Faraday method with a sensitive balance described by Poulis et al. (6). The sample consisted of 0.2841 gram of PAA held in an evacuated spherical quartz container. Measurements were made at fields of 2550, 1050, 275, and 200 oersteds at a number of temperatures in the liquid crystal and liquid phase. The absolute accuracy of the susceptibility measurements was about 3%, determined by the irreproducibility in the adjustment of... 

Magnetic Susceptibility Measurements. The magnetic susceptibility of the solids was measured by the Faraday method with Hg[Co(SCN)4] used as the calibrant. Corrections for diamagnetism were made using Pascals constants. Solution measurements were made in CHCI3 by NMR techniques (17),... 

There will be described first the most widely used method for determination of diamagnetic and paramagnetic susceptibilities, namely the method of Gouy. Second, a very satisfactory alternative method, that of Faraday, will be described briefly. Third, reference will be made to possible methods for studying the magnetic properties of catalysts in situ, that is, while they are actually being active. And last, a method... 

Fig. 7.3. Internally pressured cell for magnetic susceptibility measurements of fluid selenium by the Faraday method (Freyland and Cutler, 1980). The sealed quartz capsule containing the sample is mechanically supported by the surrounding molybdenum pressure cell.

The standard method for the determination of magnetic susceptibilities of diamagnetic samples is the Faraday-Curie method [8]. The method is based on the measurement of the force on a sample with susceptibility X in an inhomogeneous magnetic field. For diamagnetic substances... 

Magnetic circular dichroism (MCD) spectroscopy is a type of electronic spectroscopy, also called the Faraday effect or the Zeeman effect, that can be a particularly useful and effective method for structural analysis. For example, MCD can be used to assign the transitions in the electronic absorption spectrum (UV-visible), with respect to details such as the molecular orbital origins of the transitions. Often, such transitions are not clearly observed in the UV-visible spectra, because they are spin-forbidden and weak, but upon application of the magnetic field, Hq, they can be detected. MCD spectroscopy can also be used to determine not only the spin state for a metal such iron, but also the coordination number at the metal. 

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