Earth Planets Space, Vol. 65 (No. 3), pp. 193-197, 2013
T. Takeuchi, K. Hisayoshi, and C. Uyeda
Institute of Earth and Space Science, Graduate School of Science, Osaka University, Toyanaka, Osaka 560-0043, Japan
(Received December 1, 2011; Revised May 15, 2012; Accepted May 15, 2012; Online published March 12, 2013)
Diamagnetic anisotropy ΔχDIA was detected on a submillimeter-sized calcite crystal by observing the rotational oscillation of its magnetically stable axis with respect to the magnetic field direction. The crystal was released in an area of microgravity generated by a 1.5-m-long drop shaft. When the oscillations are observable, the present method can measure ΔχDIA of crystal grains irrespective of how small they are without measuring the sample mass. In conventional Δχ measurements, the background signal from the sample holder and the difficulty in measuring the sample mass prevent measurement of ΔχDIA for small samples. The present technique of observing ΔχDIA of a submillimeter-sized single crystal is a step toward realizing ΔχDIA measurements of micron-sized grains. The ΔχDIA values of single micron-sized grains can be used to assess the validity of a dust alignment model based on magnetic torque that originates from the ΔχDIA of individual dust particles.
Key words: Dust alignment, diamagnetic anisotropy, magnetic rotational oscillation.