Magnetometry

However they are measured, the data are manipulated (with knowledge of the molar weight, and estimations of diamagnetic corrections for sample and holder) to give M, which is determined as a function of T and/or H. 

the useful plots of x (usually calculated as MJH), xT and x T at fixed H, and M vs H at fixed (usually low) T, can be constructed. These data can provide a wealth of information on exchange coupled clusters. An increase in xT as T decreases is a signature of low lying states with big spin 

It is often the case that %T does not plateau at low temperature, even when only the ground state is populated. This can be a function of ZFS of the ground state, intermolecular interactions, or both. For samples with large magnetic anisotropy the crystallites may torque in the applied magnetic field and give readings different from those expected on the basis of Equation 5.1. 

It is generally safer to take the ground state spin from the saturation value ofMvsH at the lowest temperature available. Here the assumption 

If only the ground state is populated in the low temperature range, then M(H,T) data can in principle be modelled to determine the ZFS. However, excited state population can have similar effects and often there is not a unique fit to the data. ZFS parameters are more safely determined by spectroscopic methods (see below). 

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Stoichiometric reaction of 5 with phenylsilane produced the iron(O) bis(silane) c-complex 18, which was confirmed by the single-crystal X-ray analysis as well as SQUID (Superconducting QUantum Interference Device) magnetometry (Scheme 19). Complex 18 as a precatalyst showed high activity for the hydrosilylation of 1-hexene. 

Figure 5.14 XMCD derived magnetizations for Cr3+ (a), Dy3+ (b) and the complex magnetization obtained by bulk magnetometry (c) for the DyCrDy complex. (Reprinted with permission from [47]. Copyright 2012, Royal Chemical Society.)...

Figure 7.18 Magnetization isotherm of [Tb2] at 0.26 K as measured through (iHall magnetometry. Solid and dashed lines are the calculated behaviours for collinear and...

A bomb can be considered to contain four functional blocks, namely, a control system, a detonator, a booster, and a main charge. Although a simple ignition fuse can be used as a control system and timing device, the control system is usually more mechanical or electrical in nature. The detection of control systems may be visual, or by magnetometry, or by X-ray. It must be remembered that many of the items involved in the ignition system, that is, clockwork, batteries, or electronic circuitry, are commonplace in ordinary items, such as cameras, mobile telephones, and personal stereos, and are not unique indicators of the presence of a bomb. In fact, it is the presence of explosives that is the key indicator of a bomb. 

Dependence of the Crystal Radius and of the Magnetization Obtained by Relaxometry AND Magnetometry with the [Fe ]/[Fe ] Ratio... 

Ms reiaxo IS the Specific magnetization calculated from NMRD curves, magneto IS the radius obtained from magnetometry. 

Ms magneto IS the Specific magnetization obtained from magnetometry. 

Magnetometry curves of a ferritin sample at different temperatures are shown in Pig. 14. Two contributions can be noticed the first one saturates at high magnetic field, while the second one increases linearly with the field. At room temperature, the magnetometry curve is almost linear with the magnetic field the magnetization of ferritin shows no saturation up to 5T and remains simply proportional to the applied field, as for a simple... 

The PEDM is able to explain the anomalous relaxation of solutions of ferritin and akaganeite particles, especially its linear dependence with Bq, the external magnetic field. The model is compatible with the observed dependence of the rate on pH. The relaxation rate predicted by the PEDM is proportional to the number of adsorption sites per particle (q) the values deduced for q from the adjustment of the model to experimental results (from NMR and magnetometry in solutions) are reasonable for hydrated iron oxide nanoparticles (63). 

The magnetic properties of iron oxides can be determined using Mossbauer spectroscopy, neutron powder diffraction and magnetometry (see Chap. 7). The characteristic parameters are the magnetic moment, the permeability, the saturation magnetization, the magnetic anisotropy constants and the Bhf (Tab. 6.2). 

This chapter reviews the various methods used to identify and characterize iron oxides. Most of these are non-destructive, i. e. the oxide remains unaltered while being examined. These methods involve spectroscopy, diffractometry, magnetometry and microscopy. Other methods, such as dissolution and thermal analysis destroy the sample being examined. Only the principle of each method is given here. The main weight is put on the information about Fe oxides which can be extracted from the analytical results obtained by the different techniques together with references to relevant studies. A detailed description of each technique can be found in the appropriate texts listed in each section. 

Both Mbssbauer spectroscopy and magnetometry are based on the magnetic behaviour of (essentially) iron in a crystal structure, but operate on different dimensional scales. Whereas Mbssbauer spectroscopy yields information about charge and coordination, magnetometric methods are more sensitive to the type of magnetic coupling and to the magnetic domain status of particles. 

Molecular mechanics calculations " suggested that the molecule is planar, but later Hartree-Fock computations concluded that the two allyl units are twisted with respect to each other by 25°. Recently, Matsuda and Iwamura used magnetometry (see Section 8) to show that the singlet and triplet states of 2,3-dimethylene-1,3-cyclohexadiene (36) are degenerate. This finding accounts for the observed linear Curie plot, which was previously interpreted as indicative of a triplet ground state. 

An increasingly important tool to determine the strain-induced anisotropy is MOKE (magneto-optical Kerr effect). In section 2 we mentioned already the calculations by Freeman et al. (1999). Experimentally, e.g. Ali and Watts (1999) (see also references therein) apply a bending device to induce strains in a controlled way, and determine the (local) curvature and the strains by optical interferometry or by direct measurement (stylus). The properties of the substrate are incorporated in a finite-element modelling calculation, thus allowing an absolute determination of the film properties. Compare also Stobiecki et al. (2000), who studied the strain induced anisotropy in FeB/Cu/FeB trilayers, using Kerr magnetometry (MOKE). 

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