Based on our results of EPR experiments, we point out that KCuF3, a onedimensional Heisenberg antiferromagnet in spite of its pseudo-cubic crystal structure, has a Dzyaloshinsky-Moriya (DM) antisymmetric exchange interaction Xd,JS, X S, between spins on the c-axis; the direction of d,J is perpendicular to the c-axis. The observed EPR linewidth shows (2 + sin2 @)-like angular behaviour (6 is the angle between the c-axis and the external field), which coincides well with the theory of line broadening due to the DM interaction with d , i c-axis. The linewidth shows a rapid decrease with lowering temperature and its value extrapolated to T = 0 K from the paramagnetic region is zero. As the theory by Soos et a1 shows, this temperature dependence also indicates that the EPR line is governed by the DM interaction; i.e., it arises from the four-spin correlation functions ((SpSf -SPSP)') (where cr andP = x , y and z ) in the second moment due to the DM interaction which is different from ((SpSf + SfSp)') of the perturbation terms of both the dipole-dipole and the anisotropic exchange interactions.

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Structure D 2000The Crystal Structure of LiND2 and Mg(ND2)2. -The crystal structures of the title compounds are determined by high resolution powder neutron and synchrotron X-ray diffraction. LiND2 crystallizes in the tetragonal space group I4 with Z = 8. The Li + ions are tetrahedrally coordinated by four ions. Mg(ND2)2 crystallizes in the tetragonal space group I41/acd. The cation is again tetrahedrally coordinated by four amide ions. The metal amides LiNH2 and Mg(NH2)2 are compounds which may play important roles for designing new high-performance hydrogen storage materials. -(SOERBY*, M. H.; NAKAMURA, Y.; BRINKS, H. W.; ICHIKAWA, T.; HINO, S.; FUJII, H.; HAUBACK, B. C.; J.

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