The crystal structure and magnetization of nanoscale enTMOS–Fe2O3 sol–gel composites with weight iron concentration x, varying from 0.003 to 0.065, have been studied by the transmission electron microscopy technique and a superconducting quantum interference device magnetometer. The clusters are crystallized in a hexagonal crystal structure. All the samples demonstrate a superparamagnetic behavior with antiferomagnetic cluster–cluster coupling at low temperature. The effective paramagnetic moment, μeff, has been found to vary in the range from 5.9 (S=5/2) to 2.5 μB per iron ion. The concentration dependence of the μeff shows a minimum for x∼0.01. At a low iron concentration x<0.01, μeff is practically independent of x and equals about 6 μB per Fe ion. The concentration interval 0.01<x<0.07 is characterized by a monotonical increase of μeff from 2.5 to about 3 μB per Fe ion. Thus, an abrupt variation of μeff (about two times) is observed at x≈0.01. It has been shown that such behavior can be caused by competition between the uncoupled “surface” and antiferromagnetically coupled “bulk” Fe magnetic moments.