Magnetic properties minerals

Spinel ferrites, isostmctural with the mineral spinel [1302-67-6] MgAl204, combine interesting soft magnetic properties with a relatively high electrical resistivity. The latter permits low eddy current losses in a-c appHcations, and based on this feature spinel ferrites have largely replaced the iron-based core materials in the r-f range. The main representatives are MnZn-ferrites (frequencies up to about 1 MH2) and NiZn-ferrites (frequencies 1 MHz). 

Minerals normally considered nonmagnetic may be rendered magnetic by elemental substitution of a small amount of a magnetic element in the crystal lattice. Magnetic properties may also be affected by partial alteration in weathering effects. 

With respect to magnetic properties, the intrinsic magnetic susceptibiHty of pure chrysotile is very weak. However, the presence of associated minerals such as magnetite, as weU as substitution ions (Fe, Mn), increases the magnetic susceptibiHty to values around 6 x 10 m /kg. With amphiboles, the magnetic susceptibiHty is much higher, mainly because of the high iron content typically, amosite and crocidoHte exhibit susceptibiHty values of 100 and 75 X 10 m /kg, respectively (23). 

Coey, J.M.D. (1988) Magnetic properties of iron in soil iron oxides and clay minerals. In Stucki, J.W. Goodman, B.A. Schwert-mann, U. (eds.) Iron in soils and clay minerals. D. Reidel Publ. Co., 397-466... 

Itoh, H. Sugimoto,T. (2001) Synthesis of monodispersed magnetic particles by the gel-sol method and their magnetic properties. Stud. Surface Sci. Catalysis 132 251-254 Iwasaki, 1. (1978) Selective flocculation of fine grained iron bearing materials. In Somasun-darun, P. Arbiter, N. (eds.) Benefication of mineral fines. Problems and research needs. New York, 257-262... 

Murad, E. (1996) Magnetic properties of microcrystalline iron(III) oxides and related materials as reflected in their Mossbauer spectra. Phys. Chem. Miner. 23 248-262... 

The mineral magnetite may be characterized from its physical and magnetic properties and by x-ray methods. The iron content in the oxide may be determined by AA, ICP/AES, x-ray fluorescence and other instrumental techniques (See Iron). 

Complex bimetallic quinary compormds Ba2CaM M Fi4 and Ba7M M F34 with stmctures built from interconnected rings of four or eight octahedra, respectively, attracted interest because of their low-dimensional magnetic properties when appropriately substituted by transition metal ions (see recent survey in Refs. 157 and 158). The basic chain elements derived from the minerals usovite and jarlite are shown in Figure 35. 

Table 6.5. Electrical and magnetic properties" of thiospinel minerals... 

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