Measuring magnetic susceptibilities of nanogram quantities of materials using microcantilevers

We describe a novel technique For measuring magnetic susceptibilities of na nogram quantities of magnetic materials that utilizes the extreme force sen sitivity of microcantilevers. The magnetic force acting on samples attached to the free end of a cantilever can be measured as changes in the resonanc e response of the cantilever. The shift in resonance frequency of the canti lever is proportional to the field gradient, whereas the deflection of a ca ntilever is proportional to the magnetic force. The magnetic susceptibility measurement is based on comparison of the forces acting on the sample and a reference material in the same magnetic field and field gradient. We have determined the magnetic susceptibilities of nanogram quantities of many pa ramagnetic materials. The measured magnetic susceptibilities show excellent agreement with values found in the literature. (C) 2001 Elsevier Science B .V. All rights reserved.