Epithermal neutron diffraction from Gd compounds

The neutron diffraction from natural Gd alloys has been performed with a TOF type epithermal diffractometer installed at a pulsed neutron source produced by a 300 MeV electron linac. The TOF diffraction spectra have been observed with a good S/N ratio of 200, if the epithermal neutron with an energy of 1 eV has been used. The nuclear scattering amplitude bsub(Gd) of natural Gd which is independent of neutron energy for epithermal neutrons was determined by following three methods: 1) by comparing the intensity of Bragg reflection from Gdsub(0.9)Ysub(0.1) with those obtained from KBr and Cu, 2) by comparing the intensity of the magnetic reflection from Gd with that of nuclear Bragg reflection, 3) by comparing the intensity of the 200 fundamental reflection with that of the 100 superlattice reflection from an ordered alloy of GdZn. The scattering amplitude bsub(Gd) thus obtained is (0.95 +- 0.04) x 10-12 cm. The neutron diffraction from a single crystal of Gdsub(0.85)Thsub(0.15) has detected magnetic satellites around the 002 Bragg reflection at 80 K, suggesting that a helical spin structure with a period of 6.2 layers propagating in the c axis is developed in the crystal