Rev. Sci. Instrum 53(9) 1344-1354

Detection coil, sensitivity function, and sample geometry effects for 
vibrating sample magnetometers

A. Zieba and S. Foner

A general description based in the sensitivity function is presented for 
the effects of detection coil geometry and sample geometry on the output 
of a vibrating sample magnetometer (VSM). This harmonic function gives the 
VSM output versus position of a vibrating diploe. Calculations of the 
sensitivity function for axial and transverse detection coil 
configurations are presented using exact results and approximation 
including a spherical harmonic expansion. For axial, thick, rectangular 
cross-section coils, the design yielding the output with a minimum 
sensitivity to sample position, sample shape and sample size is presented. 
For the transverse geometry the small coil approximation is used. Various 
designs yielding maximum output and output insensitive to variations of 
sample geomtery are reviewed. The signal-to-noise for various coil 
configurations is also discussed. Corrections for the VSM output are 
derived for "large" samples with regular geometries (thin rod, circular 
cylinder, cube, and rectangular prallelepiped). The calculations were 
verified experimentally for rod-like sample for different orientations. 
The effects of applied field homogenity, sample position errors, and 
sample support contributions are also discussed. Finally, applications of 
the analysis to other types of induction and force type magnetometers are 
discussed briefly.