Discontinuous shear thickening is usually observed in very dense suspensions of particles and manifests by a jump of shear stress at a given shear rate that we call the critical shear rate or by a decrease of the shear rate during a ramp of stress. This transition is believed to be created by the sudden formation of a percolating network with frictional contacts between the particles and happens when the shear forces dominate the repulsive forces which keep the particles apart. These repulsive forces can be due to ionic or to polymer layers adsorbed on the surfaces of the particles. Our aim here was to be able to control this transition thanks to the application of a magnetic field