X-RAY LINEAR BIREFRINGENCE AND LINEAR DICHROISM IN A COBALT CRYSTAL MEASURED WITH A TUNABLE X-RAY POLARIMETER

X-ray linear birefringence and linear dichroism spectra have been meas ured simultaneously and quantitatively for the first time. The sample was a hexagonal cobalt single-crystal foil. The apparatus used was an energy-tunable X-ray polarimeter, consisting of a polarizer, a phase r etarder and an analyser. The X-ray energy was scanned over a range of 350 eV near the K-absorption edge. The Kramers-Kronig relation between the refraction and absorption anisotropy has been confirmed on an abs olute scale. The phase-difference sensitivity of the polarimeter as a polarization inferometer is as small as 2 pi/10000, which is about 100 times smaller than that of the Bonse-Hart inferometer.