  A potassium alumina borosilicate glass with the composition
13K2O*13Al2O3*16B2O3*43SiO2*15Fe2O3-x was melted using Fe2O3 as raw material.
The melt was dumped from a Pt-crucible with a downpipe in water which resulted
in the formation of phase separated droplets with a size of around 100 - 150
nm. In this droplets, magnetite crystals with a size of around 10-20 nm were
observed. These magnetite nanoparticles with superparamagnetic behaviour are
arranged to larger aggregates. This leads to a higher effective magnetic
radius. According to magnetisation measurements the particles show hysteresis.
The ratio of remanent vs. saturation magnetisation is not as high as it is
necessary for uniaxial anisotropy. It is possible to elude the phase
separations by cooking the pulverized glass in concentrated sodium hydroxide.
Additional temperature dependent magnetorelaxometry (TMRX) measurements show in
the distribution of the relaxation of magnetic moments over the course of
temperature two peaks at 13 and 39 K. According to an interparticle distance
smaller than 5 dC (the core diameter) could that be a result of strong magnetic
interactions. Other magnetic relaxation processes also explain this measured
effect.
