Andrew Boothroyd

Abstract:

The spin ordering of La3/2Sr1/2NiO4 was investigated by magnetization measurements and by unpolarized and polarized-neutron diffraction. Spin ordering with an incommensurability ε≈0.445 is observed below TSO∼80 K. On cooling, a spin reorientation is observed at 57±1 K, with the spin axes rotating from 52° ±4° to 780°±3°.

Abstract:

We present a neutron-diffraction study of the crystal structure and magnetic ordering of PrO2. The magnetic moment of the Pr4+ ion is determined from separate single-crystal and powder measurements, and both values are found to agree with a previous powder study. Our powder data reveal a new aspect to the magnetic structure: a doubling of the magnetic unit cell along one crystal axis.

Abstract:

We report preliminary results of a neutron inelastic scattering study of the magnetic excitations in single-crystal PrBa2Cu3O6+x (x approximate to 0.93). The measurements probe (i) the dispersion of the low-energy crystal field levels of the Pr ion in the low-temperature AFIII magnetic phase and (ii) the Cu optic spin wave mode gap in the AFI magnetic phase. We compare the results with previous measurements made when the same crystal was in an oxygen-deficient state, and thus establish the effect of hole doping on the magnetic excitations.