  We synthesized and characterized the colloidal suspensions of $FeO \cdot
Fe_{(2-x)}Nd_{x}O_{3}$ nanoparticles with $x=0.00, 0.02, 0.04, 0.06 \text{ and
}0.1.$ The effect of the $Fe^{3+}$ ion replacement by $Nd^{3+}$ on the crystal
structure is in-depth studied, through X-ray diffraction (XRD) and the obtained
cation distribution. The magnetic properties of the synthesized $FeO \cdot
Fe_{(2-x)}Nd_{x}O_{3}$ nanoparticles also were investigated and corroborated by
other physical methods. A remarkable saturation magnetization of 105
$Am^{2}/kg$ was achieved for $x=0.06$.
