Magnetic field measurements

The special feature of the spin crossover process in all bpym-bridged dinuclear compounds studied so far is the occurrence of a plateau in the spin transition curve. A reasonable assumption to account for this observation is that a thermal spin transition takes place successively in the two metal centres. However, it cannot be excluded that spin transition takes place simultaneously in the dinuclear units leading directly from [HS—HS] pairs to [LS-LS] pairs with decreasing temperature. Therefore, two possible conversion pathways for [HS—HS] pairs with decreasing temperature may be proposed [HS—HS]<->[HS—LS]<->[LS—LS] or [HS-HS] [LS-LS]. The differentiation of the existence of the [LS—LS], [HS—LS], and [HS—HS] spin pairs is not trivial and has recently been solved experimentally by utilisation of magnetisation versus magnetic field measurements as a macroscopic tool [9], and by Mossbauer spectroscopy in an applied magnetic field as a microscopic tool [11]. 

IX. Magnetic Field Measurement by Integration of Electric Field Around a Closed Path... 

IX. MAGNETIC FIELD MEASUREMENT BY INTEGRATION OF ELECTRIC FIELD AROUND A CLOSED PATH... 

Small Magnetic Field Measurement ofT2. If the oscillating magnetic field is small (Hi [Pg.715]

Table 8.13. Molecular parameters for the four isotopic forms ofLiBr, determined from the zero- and strong-magnetic field measurements...

The spectrometer provides two series of data as a function of time the number of detected ions and, simultaneously, a physical value indicating the mass of these ions. This can be, for example, the value of the magnetic field measured by a Hall probe in the case of a magnetic instrument. The ions of every mass appear with a certain distribution over a time period, as shown in the sketch. The surface under the curve is proportional to the number of detected ions, while the value of the magnetic field at the centroid of the peak is an indicator of the ion mass. This centroid and mass must therefore be determined. In order to achieve... 

Figure 14.5 The profile of the magnetic field measured at the center of an electrode at various distance from the electrode.

Each elementary current loop produces a magnetic field which is proportional to S. The magnetic field of the current distribution is the sum of the magnetic fields of the elementary loops. The relation between S and B can be formulated as a convolution because the magnetic fields of the elementary current loops are equally shaped. The relation between the z-component of the magnetic field measured with a coil and S can be written as ... 

Unless noted otherwise, parameters are for Br and were carried out using single crystals and in the absence of an applied magnetic field. Measured by Klaassen et al. ... 

An example of a vector product is the force on a moving charged particle due to a magnetic field. If q is the charge on the particle measured in coulombs (C), v is the velocity of the particle in meters per second, and B is the magnetic induction (often called the magnetic field ) measured in tesla (T), the force in newtons is given by... 

Simplicity of this model allows us to investigate not only frequency responses of the magnetic field, measured by a receiver, but also a distribution of currents in a conducting medium. Such will help us to understand deeper physical principles of the induction logging as well as some approximate methods of calculation of fields which are widely used for interpretation. 

Therefore, the ratio of amplitudes as well as the difference of the phases of the magnetic field measured by two probes do not depend on electrical properties and the borehole radius (a 3> 1). 

As is well known, if the moment of the transmitter coil changes as a step function with time, induced currents appear in the surrounding medium. At the beginning they are concentrated in the borehole, but with an increase of time their intensity increases at larger distances from the coil, and always there is such moment when they are practically located in the formation and their magnitude is defined by the conductivity of the external area, i.e. the formation. For this reason the magnetic field measured on the borehole axis, starting from this moment, does not practically differ from that in a uniform medium with the formation conductivity. 

A similar situation occurs in the presence of the invasion zone even when its conductivity is greater than that of the formation. Inasmuch as at the late stage of the transient response, induced currents are practically absent in the borehole and in the invasion zone the magnetic field, measured by a receiver, is not dependent of the position of the probe with respect to the borehole axis and caverns, as well as of the distance between the coils of the probe. At relatively large times induced currents are located far away from the... 

Zeeman-Doppler imaging technique [32,37] is the preferred method to measure magnetic fields on the surfaces of rapidly rotating stars, however, FFZM technique is more robust and effective for global magnetic field measurements on slowly rotating stars (especially, in the case of weak magnetic fields). 

To end this section, we mention that the narrow ESR line, its anisotropic and field-independent g-factor, and the excellent chemical stability of highly-purified (Fa)2PF6 crystals can be used for very precise magnetic field measurements as well as for the stabilisation of ESR spectrometers [38]. For magnetic-field measurements, in a range between the terrestrial magnetic field and several Tesla, a field resolution of at least 10" Tesla was achieved. For the stabilisation of the field/frequency ratio BqIvesr, a stability of 10" was obtained [34]. 

H 1) Magnetic field, measured in Am . 2) Henry SI unit of magnetic inductance. 

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