Orbital anisotropy in paramagnetic manganese oxide nanostripes

We have detected a clear magnetic anisotropy in the temperature and field dependent Mn L-2,L-3 magnetic circular dichroism (MCD) spectra of 28 angstrom wide paramagnetic manganese oxide nanostripes, which we relate to the presence of a largely unquenched orbital moment revealed by MCD sum rule analysis. Polarization, angle, and temperature dependent linear dichroism spectra indicate that the observed anisotropy is related to a depletion of 3d states with m(l) = +/- 2 orbital quantum number in the ground state of the paramagnetic system. Strongly anisotropic electrostatic coupling provides an internal source of spatial symmetry breaking which might generally yield paramagnetic anisotropy phenomena in 3d oxide nanostructures.