Physik-Praktikum für Vorgerückte an der ETH Zürich: "Nachweis antiferromagnetischer Fernordnung mittels Neutronendiffraktion"
"Determination of long range antiferromagnetic order by powder neutron diffraction"

Antiferromagnetic (AFM) ordering of Mn spins in manganese sulfide MnS or manganese oxide MnO will be determined by powder neutron diffraction. These compounds crystallize in a rock salt face centered cubic crystal structure. Manganese sulfide MnS shows a transition to the AFM state with the propagation vector k=[1/2 1/2 1/2] at Neel temperature about 150K. The Mn-spins forming planes perpendicular to the body diagonal are ferromagnetically aligned, whereas the spins in the neighboring planes are antiparallel.

During the practicum we will try to reproduce the one of the neutron diffraction experiments performed during 1946-1951 for which C.G. Shull was honored with the Nobel Prize in 1994. We will perform neutron diffraction experiment with MnS using powder diffractometer HRPT/SINQ. From the analysis of the nuclear and magnetic Bragg peak intensities and positions we will verify the crystal and magnetic structures of manganese sulfide and determine the size of the magnetic moment on manganese.

Note: The practicum is performed during only one day at PSI. To perform the experiment effectively and analyze the experimental data it is necessary to have basic theoretical background on mathematical description of crystal structure and diffraction (reciprocal space, Brillouin zone, structure factor, etc.)

Some relevant lectures.

V. Pomjakushin, Last modified: 25 March 2010 19:54:49 CET