Synchrotron radiation topographic study of the thick ferromagnetic-fan interface in MnP

The coexistence of the ferromagnetic and fan phases in a (001) MnP crystal, under a magnetic field applied along the b direction, is investigated in real time, by synchrotron radiation diffraction topography, at T approximate to 48 K. The ferromagnetic-fan interface includes bulk transition regions, elongated along a, and thick enough along the b direction (in the 10(-4) m range) to produce a substantial contribution to diffraction. The Bragg condition changes continuously across these regions. This configuration, which involves magnetic charge distribution, is in sharp distinction with the usual two-dimensional character of magnetic walls and phase boundaries. The thick interface is likely to comprise a set of intermediate magnetic states.