The maximum thermal remagnetization (TR) after de-demagnetization was studied at sintered RE/T hard magnets and at barium ferrite. We found very large TR-effects for SmCo5, large effects for hard ferrites, medium for NdFeB and a very low effect for Sm2Co17 magnets. The experimental results are interpreted on the basis of a theory taking into account the local fluctuations of the internal magnetic field as well as the internal demagnetization effects. The relevant model parameters were estimated for SmCo5 and barium ferrite.