Figure 5: The examples of the dependence of the absorption lines derivatives, 𝑑 𝜒 / 𝑑 𝐻 d c , on dc magnetic field 𝐻 d c . The spectral lines were recorded for three different samples of porous glass of type B in the case when magnetic nanoparticles filling the samples come from the magnetic aqueous suspension with pH value 7.92, 8.78, and 9.04, respectively.