Disclaimer: I'm just computer scientist.
I'm planning a simple experiment that uses a coil to measure a small varying magnetic field. How small ? I don't know yet. I'm exploring the unknown. All I know is that other people claim they made it with a 300 Ohms coil that had a 6mm diameter soft iron core. That is all the information I have. I don't know the wire gauge, the number of turns, or the coil dimension.
In order to try reproducing this experiment I would like to know if I should better use a ferrite core or an soft iron core. The frequency are low, below 20kHz.
Another question is the diameter. Will I gain in sensibility with a larger core diameter ?
It is surprisingly difficult to find soft iron cores. I found some in China and the smallest diameter is 10mm. I found ferrite cores of 8mm diameter.
I know that soft iron is easier to cut at the right dimension. I read that ferrite falls appart when we try to cut it with a conventional saw.
A last question is if the inductance of a coil is a directly linked to the sensibility to varying magnetic field. In other words, may I assume that the higher the inductance, the more sensible to magnetic field my coil will be ?
EDIT The output voltage of the coil is described to be in the microvolt range.