Active Microlevers as Miniature Torque Magnetometers

Copyright © (1996) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics

An extremely sensitive miniature torque magnetometer using Si $p$-doped piezoresistive cantilevers is described. The magnetization $\vec{m}$ of very small magnetic or superconducting samples ($\leq$1~$\mu$g) deposited on the cantilever can be measured via the torque $\vec{\tau }=\vec{m}\times \vec{B}$ produced on them by an applied field $B$. The high resolution in the lever deflection of the order of 0.1~\AA{} corresponds to a torque sensitivity of better than $\Delta \tau \leq 10^{-14}$~Nm. In a homogeneous field of 1~Tesla this device allows magnetic moments as small as $\Delta m\simeq 10^{-15}$~Am$^2$ to be measured, a value far higher than that measurable by the best commercial SQUID magnetometers. Measurements performed on microcrystals of the high-$T_{\rm c}$ superconductors Bi$_2$Sr$_2$Ca$_1$Cu$_2$O$_8$ and Hg$_1$Ba$_2$Ca$_3$Cu$_4$O$_{10}$ in the static and dynamic modes demonstrate the excellent performance of this device at low temperature and in magnetic fields ranging between a few millitesla and 5~Tesla.

By: C. Rossel, P. Bauer, D. Zech (Univ. Zurich, Switz.), J. Hofer (Univ. Zurich, Switz.) and H. Keller (Univ. Zurich, Switz.)

Published in: Journal of Applied Physics, volume 79, (no 11), pages 8166-73 in 1996

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