Units magnetic quantities

The dimensions of units in electricity and magnetism are the origin of much confusion. In the days when mechanical and thermal quantities were expressed in cgs, two different systems were introduced for the electrical and magnetic quantities. They are the esu (electrostatic units) and the emu (electromagnetic... 

We shall use mainly the cgs Gaussian system of units. This is a mixed system with electrical quantities measured in cgs electrostatic units (esu) and magnetic quantities measured in cgs electromagnetic units (emu). 

Magnetic quantities are defined in much the same way as electric quantities. The unit magnetic pole is such that two of them, one centimeter apart in a vacuum, repel each other with a force of one dyne. The strength of a magnetic field is taken to be equal to the force in dynes on a unit pole put in the field. 

Quantities and Units-Part 0 General Principles Units and Symbols Quantities and Units-Part 1 Space and Time Quantities and Units-Part 2 Periodic and Related Phenomena Quantities and Units-Part 3 Mechanics Quantities and Units-Part 4 Heat Quantities and Units-Part 5 Electricity and Magnetism Quantities and Units-Part 6 Light and Related Electromagnetic... 

In the context of attempts to use only units based on the SI system an alternative definition of atomic units was proposed. One starts from the SI system (with 4 basic units), and measures then mass, electric charge, action and quantities of the dimension of the dielectric constant of the vacuum in units of m, e, h, and 47reo respectively. On this way one arrives at the same Hamiltonian in atomic units, as following Hartree - as long as no magnetic quantities are involved. We must therefore reconsider the system of units, when we come to electrons in the presence of magnetic fields (section 2,10). 

For definitions of the concepts and magnetic quantities used here (the primary system of units in this chapter is CGS) and discussions of different magnet materials see other articles in this Handbook (Zijlstra 1982, Stablein 1989, Buschow 1988), also general textbooks on magnets (e.g., McCaig 1977, Burzo 1986). The textbook by Burzo has an exhaustive bibliography on the REPM, current as of 1985. 

Table A.2 Derived units (examples only the list can be continued, e. g. magnetic quantities). for electric and...

Gaussian units A system of units for electric and magnetic quantities based upon c.g.s. electrostatic and electromagnetic units. Although replaced by S1 units in most branches of science, they are, like Heavi-side-Lorentz units, still used in relativity theory and in particle physics. In Gaussian units, the electric and magnetic constants are both equal to unity. 

In many situations the application of an external electric or magnetic field on a substance can instigate a response which is referred to as polarization . Usually, the response is proportional to the applied field, which is called linear response. We refer to the polarization of electric quantities as simply the polarization and to the polarization of magnetic quantities as the magnetization. We will also refer to the polarization or magnetization of the unit volume (or elementary unit, such as the unit cell of a crystal), as the induced dipole moment p(r) or the induced magnetic moment m(r), respectively. 

Cobalt. There is no U.S. mine production of cobalt. Refining of imported nickel—cobalt mattes has not occurred since the mid-1980s. About 1600 t of secondary cobalt was recycled from scrap by 13 faciUties in the United States representing - 22% of total U.S. consumption. The price of the metal was around 44/kg. Most is imported from Zaire and Zambia. Increasing quantities are coming from Russia. Historically, the price of cobalt has been quite volatile and dependent on the pohtical environment in those countries. Cobalt is used in superaHoys, 40% catalysts, 14% paint driers, 11% magnetic alloys, 10% and cemented carbides and other uses, 16%. 

Rather than quote some (mass normalized) force on the sample at each of several field strengths, it is sufficient to report the slope of the linear part of the curve in Fig. 5-6. This slope is called the magnetic susceptibility of the sample. Units for susceptibility, x > and related quantities to be discussed in this section are reviewed in Box 5-3. 

Scientists measure many different quantities—length, volume, mass (weight), electric current, temperature, pressure, force, magnetic field intensity, radioactivity, and many others. The metric system and its recent extension, Systeme International d Unites (SI), were devised to make measurements and calculations as simple as possible. In this chapter, length, area, volume, and mass will be introduced. Temperature will be introduced in Sec. 2.7 and used extensively in Chap. 11. The quantities to be discussed here are presented in Table 2-1. Their units, abbreviations of the quantities and units, and the legal standards for the quantities are also included. 

The quantity gNI is commonly called the nuclear magnetic moment and is listed as such in tables actually, gNI is not the magnitude of ftN, but rather is the maximum z component of nN in units of nuclear magnetons. 

It is convenient for many purposes to have a quantity which summarizes magnetic properties and which is, ideally at least, independent of temperature. We define the magnetic moment , in units of the Bohr magneton ... 

With most lines, however, ail anomalous Zeeman effect is observed and the number of components is greater, in some cases reaching twelve or fifteen. They are symmetrically arranged and symmetrically polarized. The displacements, as in the simpler case, are proportional to the magnetic field intensity H, and are always e xpressible, in wave numbers, as rational multiples of the displacement in the normal effect, which is 4.67 x 10 5H (reciprocal centimeter), a quantity known as the Loientz unit. The Zeeman effects observed in sun spots give valuable information as to the magnetic conditions in those areas. 

Chemical shift (8) A dimensionless quantity defined as 8 = (Vsample - vreference)/v0 X 106, where vsample is the resonance frequency of the sample, vreference is the resonance frequency of the reference, tetramethylsilane (TMS defined as zero), and v0 is the observing frequency (e.g., 300 or 600 MHz). The unit for the 8 scale is ppm (parts per million) and is independent of the strength of the applied magnetic field. Exact resonance frequency of a nucleus is a function of the environment (chemical/magnetic) of the observed nuclei. 

---