The temperature dependence of the magnetization of a light emitting diode having aferromagnetic contact (spin-LED) is measured from 2 to 300 K in magnetic fields from 30 to70 kOe and it is found that it originates from the GaAs substrate. The magnetization ofGaAs comprises a van Vleck-type paramagnetic contribution to the susceptibility whichscales inversely with the band gap of the semiconductor. Thus, the temperaturedependence of the band gap of GaAs accounts for the non-linear temperature dependentmagnetic susceptibility of GaAs and thus, at large magnetic fields, for the spin-LED.