I am using a Wayne Kerr 6500B Precision Impedance Analyzer to measure the capacitance (C) of a ferrite sample over a frequency range of 100 Hz to 120 MHz. The observed behavior is as follows:

Capacitance starts at 5 nF at 100 Hz and decreases to 0 by 1 kHz.

It remains at 0 from ~1 kHz to ~6 MHz.

At ~6 MHz, there is a slight increase in capacitance, followed by a sharp drop and blank readings between ~8-9 MHz.

After ~9 MHz, the capacitance shows a random pattern up to 120 MHz.

Additionally, repeated measurements show variability:

The first scan starts with 5 nF at 100 Hz.

The second scan shows 2.2 nF at 100 Hz, with subsequent scans exhibiting different initial capacitance values.

I am seeking to understand the potential causes of:

The sharp changes in capacitance at higher frequencies.

The random capacitance pattern observed beyond 9 MHz.

The variability in initial capacitance across multiple scans.

Could these phenomena be inherent to the properties of ferrite materials, or might they be influenced by measurement setup factors such as parasitic effects or resonance? Any insights or suggestions are greatly appreciated.