Spectroscopy-like digitizing system - principle of working

[ricko_uk]

Hi,
I am looking to understand a spectroscopy-like system principle based on magnetic fields.

With reference to the attached picture, there is a vertical stackup comprising a coil, a sample of a material or substance above it and on top a "receiver" that can read the magnetic field amplitude.

The substance has its own electromagnetic spectrum unique to it.

Assuming a number of different frequencies are applied (either at the same time or sequentially) and the coil's magnetic field flows through the substance and reaches the receiver sensor will the receive:
1) the same spectrum "shape" of the sample or
2) its inverse or
3) something else?

In other words, for every "peak" frequency of the sample, will the received read a peak or a valley?

What about at the resonant frequency? Will the sample absorb more magnetic field energy or none and let it through?

The above is obviously assuming an ideal scenario with on ideal conditions. In practice what would the issues that come into play?

Thank you