In a method to correct a B0 field drift in a temperature map exposure obtained by magnetic resonance tomography as well as a device to implement such a method, a magnetic resonance phantom is placed at a stored, marked reference position relative to an acquisition coil. A first reference phase image of the phantom is automatically acquired in the acquisition of a first phase image of an examination subject in the unheated state. A second reference phase image of the phantom is automatically acquired in the acquisition of a later second phase image of the examination subject. The phase images are adapted to one another according to the requirements of a calibration of the associated reference phase images.