Magnet, permanent properties

Permanent magnets having properties several times superior to any other known materials were developed in 1967. Praseodymium, yttrium, samarium, lanthanum, and cerium are alloyed with cobalt in the range... 

The quantity on the left is the Fourier component of the dipole moment induced by the optical field Max(w). These equations can be generalized to mixed frequency-dependent electric dipole, electric quadrupole, magnetic dipole properties, and similar equations can be written for the Fourier components of the permanent electric quadrupole, aj8(magnetic dipole, ma(co). For static Maxwell fields similar expansions yield effective (starred) properties, defined as derivatives of the electrostatic free energies. 

Table 9. Magnetic Properties of Commercial Permanent Magnet Materials...

Table 10. Properties of Permanent (Hard) Magnet Materials ...

Chromium—Cobalt—Iron Alloys. In 1971, a family of ductile Cr—Co—Fe permanent-magnet alloys was developed (79). The Cr—Co—Fe alloys are analogous to the Alnicos in metallurgical stmcture and in permanent magnetic properties, but are cold formable at room temperature. Equivalent magnetic properties also can be attained with substantially less Co, thereby offering savings in materials cost. 

Vanadium—Cobalt-Iron Alloys. V—Co—Fe permanent-magnet alloys also are ductile. A common commercial ahoy, Vicahoy I, has a nominal composition 10 wt % V, 52 wt % Co, and 38 wt % Fe (Table 10). Hard magnetic properties are developed by quenching from 1200°C for conversion to bcc a-phase foUowed by aging at 600°C (precipitation of fee y-phase). The resulting properties are isotropic, with ca kJ/m ... 

Manganese—Aluminum—Carbon Alloys. Anisotropic Mn—Al—C permanent magnet ahoys have been developed usiag warm working (87). Properties as high as B = 0.61 T (6100 G), = 220 kA/m (2.8 kOe) and (BH) = 56 kJ/m (7 x 10 G-Oe) have been obtained. A typical ahoy... 

P. Pant and H. Stableia, "Manufacture and Properties of Columnar Alnico Permanent Magnets," presented at the World Electrotechnical Congress, Moscow, Russia, June 21—25,1977. 

Another material that has permanent magnetic properties is neodymium—iron—boron, Nd2Fe24B. For an in-depth discussion see reference 7. 

The relation between matter and ether was rendered clearer by Lord Kelvin s vortex-atom theory, which assumed that material atoms are vortex rings in the ether. The properties of electrical and magnetic systems have been included by regarding the atom as a structure of electrons, and an electron as a nucleus of permanent strain in the ether— a place at which the continuity of the medium has been broken and cemented together again without fitting the parts, so that there is a residual strain all round the place (Larmor). 

Some t T)es of atoms behave like tiny magnets. The best-known example is iron, the material used to make many permanent magnets. Experiments have shown that the magnetic behavior of atoms is caused by magnetic properties of their component parts, especially electrons. 

The magnetic properties of electrons arise from a property called spin, which we describe in more detail in Chapter 8. All electrons have spin of the same magnitude, but electron spin can respond to a magnet in two different ways. Most magnetic effects associated with atoms are caused by the spins of their electrons. Iron and nickel are permanent magnets because of the cooperative effect of many electrons. 

Perhaps the common characteristic of all contributions to this volume is the permanent concern about the intimate relationships between the structural and electronic properties. Indeed, the careful design of increasingly complex molecular and supramolecular architectures allows us now to anticipate many molecular and solid state properties, but the final solid state structures are always the results of many competing interactions. The resulting electronic properties of these radical assemblies, whether conductivity or magnetism, are always very sensitive to minute modifications of their solid state structures and one of the main difficulties through... 

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