The frequency dependence of the viscous component of the magnetic susceptibility of lunar rock and soil samples
The susceptibility of two lunar samples (a soil and a low metamorphic grade breccia) has been measured in a weak field — 0.001 Oe — and as a function of frequency from 0.032 to 1.0 Hz. The measurements were made using a superconducting magnetometer. The results show that the susceptibility decreases linearly with the log of frequency. This observation is in agreement with a theoretical model for viscous decay based on the Néel theory of single-domain and superparamagnetic grains. The relation derived agrees with a model in which there is a uniform distribution of relaxation times.