Diamagnetic anisotropy of sheetsilicates

Abstract

Abstract. The diamagnetic properties of sheetsilicates are studied by measuring the magnetic orientation of micron-sized crystals. In the case of synthetic phlogopite with the average diameter of 0.65 gm and the thickness of 0.2 gm, the alignment of the grains is achieved in the magnetic field below 35 kOe. The planes of the platy single-crystal grains were alignned parallel to the field when the alignment was achieved. The alignment of the grains is realized because the field-induced anisotropic energy, caused by the diamagnetic anisotropy in the mineral's crystal structure, exceeds thermal agitation energy in the applied field. By analyzing the field dependence of grain alignment, the diamagnetic anisotropy per formula unit, A Z, of sheetsilicate mineral is estimated even if a large single crystal is not provided. The field-induced anisotropic energy is proportional to NA)~ where N is the number of molecules in the grain.A linear correlation has been found between the A X value and the F/OH mole ratio among the measured sheetsilicates. This correlation supports the assumption that the hexagonally packed oxygen-layer in the crystal lattice induces the anisotropies of the sheetsilicates.

Magnetic alignment of nonmagnetic silicates caused by paramagnetic anisotropy: Origin of polarization observed in planetary formation region

“…The effect of parameters M, χ and T on B s , which is expected from Eq. (1), has been systematically examined by measuring common sheet-silicates, such as muscovite, talc and kaolinite (Uyeda et al, 1991(Uyeda et al, , 1993. The results of these experiments confirmed that the field of alignment could be reduced considerably by increasing M or χ , and also by decreasing T , as expected from Eq.…”

“…Alignment of micron-size crystals caused by the anisotropy of magnetic susceptibility χ was recently observed for common rock-forming silicates, namely kaolinite, talc, muscovite and biotite (Uyeda et al, 1991(Uyeda et al, , 1993. The experiment was performed at room temperature (T = 300 K) using liquid ethanol as the dispersing medium.…”

“…Partial alignment occurred by a simple balance between Brownian energy 1/2 k B T and field-induced anisotropy energy 1/2 M χ B 2 , as was first proposed by Langevin and Curie (1910); where M denotes the mass of the particle and χ describes anisotropy per unit mass. This process of grain alignment has been quantitatively studied on inorganic material, such as clay and mica minerals (Uyeda et al, 1993(Uyeda et al, , 2003(Uyeda et al, , 2005a where it was explicitly shown that alignment was controlled by χ , T and M. This result means that the minimum field intensity required to achieve alignment is predictable, provided that the numerical values of these three parameters can be determined. This mechanism of aligning nonmagnetic particles was considered to be a promising technique to develop new types of industrial material (e.g.…”

Characteristics of Paramagnetic and Diamagnetic Anisotropy which Induce Magnetic Alignment of Micron-Sized Non-Ferromagnetic Particles

“…Magnetic alignment of inorganic materials have been performed on micro-crystals of some nonmetals, such as kaolinite, talc, 5) lepidolite, fluoro-phlogopite, muscovite, 6) graphite, 7) Al 2 O 3 . 8,9) and various ceramic materials.…”

“…16) Experimental evaluations of the effects of the parameters which control the magnetic alignment process, discussed above, can be examined quantitatively by adopting the inorganic materials in the alignment experiments. [5][6][7] It was difficult, for example, to alter the value of temperature over a wide range in the experiment using a biological material.…”