Magnetic anisotropy of asbestos fibers

The anisotropy of magnetic susceptibility of single asbestos fibers is meas ured. The alignment of both chrysotile and crocidolite fibers in magnetic f ields is found to be due to the anisotropy. The average measured anisotropy of volume susceptibility is 0.40x10(-6) for chrysotile and 83x10(-6) for c rocidolite. Fiber shape effects are estimated to contribute, on average, ab out 10% and 6%, respectively, to the total anisotropy of the two types of f iber. There is no evidence of significant permanent magnetic moments. The m agnitude of the observed alignment makes the effect potentially useful in r eal-time detection of airborne asbestos fibers. The experimental technique developed in the study can be used for measuring the anisotropy of small pa rticles of well-defined shape. High sensitivity of the technique permits th e measurement of torques lower than 10(-21) Nm on particles down to picogra m mass. (C) 1999 American Institute of Physics. [S0021-8979(99)00508-3].