Four-circle diffractometer with three-axis energy analysis

Magnetic solitons in CuB2O4

Studies of magnetic structures and phase transitions, especially to incommensurate structures are dominant amongst the experiments carried out on D10. 

Magnetostatic measurements on CuB2O4 had revealed two transitions at TN = 21K and T* = 10K. The exact structures of the two magnetic phases were determined on D10 by following selected Bragg reflections with temperature (Fig. 1) and exploring reciprocal space within each phase.

The first transition is to a commensurate non-collinear antiferromagnetic structure, with a small spontaneous ferromagnetic component (Fig. 2);

the second is to a helical structure where the phase of the spins along the tetragonal c axis stays constant over a length L then changes abruptly over a short period ξ (Fig. 3).

Close to T* the magnetic structure can be pictured as a periodic structure of domains which are separated by domain walls or equivalently solitons. 
The soliton lattice is further confirmed by the appearance of higher-order harmonics and considerable diffuse scattering near the Bragg reflections.

Ref.: Roessli et al., Phys. Rev. Lett. 86, 2001, 1885-1888.