Diluted magnetic semiconductors (DMS) have become in recent years a subject of intensive experimental and theoretical investigations. The phenomenon that a polarized light irradiation produces an observable macroscopic magnetization in diluted paramagnetic crystals was investigated theoretically and experimentally. Since this effect is rather small, the light induced magnetization is determined by a novel combination of the method of optical pumping, and a superconducting quantum interference detection (SQUID). The SQUID operating at liquid helium temperature offers an excellent opportunity to perform low level measurements at an equivalent noise temperature of less than one millikelvin and low drift. Because the paramagnetic Mn-ions can't be magnetized directly by polarized optiocal pumping, the exchange coupling between the photo-excited spinpolarized conduction electrons and the Mn- centers plays the essential role. The decisive role of bandstructure details for the distribution of the initially oriented spins is discussed in detail. The experimental data for Hg1-xMnxTe are compared with model calculations and only satisfactory agreement with calculation is obtained by a mean field approach for the leading exchange mechanism, with detected signale intensities in the order of 50 - 100 pT under a noise level of 4 pT/Hz"1"/"2. (Author, shortened by G.Q.).