ABSTRACT
We report the first observation of a nonreciprocal x-ray linear dichroism caused by the time-reversal odd, real part zeta of the complex gyrotropy tensor zeta(*) which is dominated by electric dipole-electric quadrupole E1E2 interference terms. A nonreciprocal transverse anisotropy was observed in the low temperature insulating phase of a Cr doped V2O3 Mott crystal when a single antiferromagnetic domain was grown by magnetoelectric annealing along the hexagonal c axis. This new element (edge) specific spectroscopy could nicely complement x-ray magnetic circular dichroism which is silent for antiferromagnetic materials.
ABSTRACT
X-ray natural circular dichroism (XNCD) has been recently detected in the XANES region for uniaxial and biaxial gyrotropic crystals. Chiral-EXAFS (chi-EXAFS) spectra are reported for the first time over a wider energy range and are analysed in terms of multiple-scattering paths of relevant symmetry. For such heavily absorbing single crystals as lithium iodate, paratellurite or potassium titanyl phosphate, the differential absorption between left-handed and right-handed circularly polarized X-ray photons cannot be measured in transmission but gyrotropy effects can still be detected in fluorescence excitation spectra. Whereas XNCD and fluorescence-detected X-ray natural circular dichroism spectra are strictly identical for uniaxial crystals, it has been established that this was true only to the first order for biaxial crystals such as potassium titanyl phosphate.
