The series of magnetic rare-earth pyrochlore stannates R2Sn2O7 (R = rare earth, except Ce and Pm) have been investigated by powder susceptibility measurements down to T = 1.8 K. The results are compared with results for the analogous titanate series, which are well known frustrated magnets. Unlike the titanates, the whole series can be formed in the cubic pyrochlore structure. Possible experimental advantages of studying the stannates are discussed. PACS Nos.: 75.10Nr, 75.50Ee, 75.50Lk

We report the neutron scattering studies of the nuclear and magnetic structures of deuterated samples of the model two-dimensional S =1/2 Heisenberg antiferromagnets on a square lattice, ͑d 6-5CAP͒ 2 CuCl 4 and ͑d 6-5CAP͒ 2 CuBr 4 ͑where 5CAP is 2-amino-5-chloropyridinium͒. Interest in these materials stems from the fact that they have relatively weak exchange between the magnetic ions, and it is therefore possible to perturb their magnetic structures and excitations significantly in experimentally accessible magnetic fields, and thereby access new quantum disordered states. We succeeded in growing fully deuterated single crystals and determined the nuclear and magnetic structures of the bromide at 10 and 1.8 K, respectively, confirming the four-sublattice spin structure expected for systems, where both inter-and intraplane exchange interactions are antiferromagnetic. The determination of the full crystal structure of the bromide highlights the possibility that interlayer exchange may also propagate via hydrogen bonds to and through the 5CAP molecule. We also determined the critical exponents for the sublattice magnetization of the bromide and mapped out the H-T phase diagram of the chloride up to 5 T.

The series of magnetic rare earth pyrochlore stannates R 2 Sn 2 O 7 (R = rare earth, except Ce and Pm) have been investigated by powder susceptibility measurements down to T = 1.8 K. The results are compared to results for the analogous titanate series, which are well-known frustrated magnets. Unlike the titanates, the whole series can be formed in the cubic pyrochlore structure. Possible experimental advantages of studying the stannates are discussed.