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

Abstract

The effect of temperature is discussed on the magnetic-alignment process of micron-sized particles dispersed in a fluid medium, based on the experimental data compiled on various non-ferromagnetic materials having different concentrations of paramagnetic impurity ion. The fieldintensity required to achieve alignment decreased with temperature following the relation calculated from the Langevin theory, when the diamagnetic particles were free of paramagnetic ions. The rotational Brownian motion was considered to randomize the direction of the microcrystals in the theory. The above-mentioned temperature dependence was expected to occur for most of the diamagnetic oxides, since the oxides were expected to posses a finite amount of diamagnetic anisotropy according to a model proposed recently to explain the origin of anisotropy. The decease of temperature caused additional reduction on the field-intensity to achieve alignment, when finite amount of paramagnetic ion was contained in the particle. This was because the paramagnetic anisotropy increased which the reduction of temperature. The doping of paramagnetic ion on non-ferromagnetic materials in the course of processing a material expected to reduce the field intensity to achieve magnetic alignment at room temperature. The above findings, concerned with the reduction of field intensity to achieve magnetic alignment, may increase the possibility of practical applications of the phenomena of magnetic alignment. (Received June 20, 2003; Accepted November 14, 2003) Keywords: diamagnetic anisotropy, magnetic alignment at low magnetic field, temperature dependence of magnetic alignment, magnetic alignment of micron-sized particle, magneto-rotation, Curie temperature dependence of paramagnetic anisotropy, doping of paramagnetic ion, ceramic material, kaolinite, graphite

Montmorillonite alignment induced by magnetic field: Evidence based on the diffusion anisotropy of water molecules

“…When the material contains paramagnetic ions in the crystal lattice, the χ para component shows the dominant contribution to χ [29,30]. The Na-mon used in the present study contains Fe by approximately 2%.…”

“…The Na-mon used in the present study contains Fe by approximately 2%. Although χ dia shows no temperature dependence, χ para shows inverse proportion to the temperature according to the Curie law [29][30][31]. Furthermore, based on the Langevin theory on magnetic alignment [32], the strength of the magnetic field to achieve complete alignment (B s ) is defined as follows [14,27,33]:…”

Efficiency of Magnetic Alignment Found in Various Paramagnetic and Diamagnetic Solids Detected by Simple Rotational Oscillation of Sample in Microgravity

“…The Bs value of biotite was less than 1% compared to Bs observed for synthetic phlogopite free of paramagnetic ions; Bs was 36 kOe. 10) Whereas, Bs was 6.2 kOe for phlogopite with PARA ¼ 1:2  10 À6 emu/g. The three kinds of mica minerals have almost equivalent crystal structures; the materials should have similar Bs values deriving from similar amount of Á deriving from diamagnetic anisotropy if their ðÁÞ PARA were not effective.…”

“…Á was as large as 10 À5 emu/g for biotite provided that the material contained paramagnetic ions at a level below 1 mass%. [9][10][11] Here ðÁÞ PARA is proportional to concentration of paramagnetic ion. Similar relationship between concentration and ðÁÞ PARA has been observed for other oxides with the exception of crystals having cubic symmetry.…”

“…For example, ðÁÞ PARA was as large as 10 À5 emu/g when concentration of ferric ion was 1 mass% for most of the natural silicates. [9][10][11] Numerical values of Á remain unmeasured for most of the ordinary solids. In the present paper, possibility is discussed on accumulating the immense number of unmeasured Á values effectively in terms of a single principle based on rotational oscillation.…”