Magnetic interactions in 119Sn substituted for Cu in antiferromagnetic and superconducting lamellar cuprates

Moessbauer Spectroscopy (MS) studies of 119Sn were carried out in antiferromagnetic La2(Cu0.99Sn0.01)O4 (214) and in superconducting GdBa2(Cu0.99Sn0.01)3O7 (123). Non-magnetic Sn4+ substitutes for Cu if the right procedure for diffusing 119SnO2 in CuO is carried out. Studies performed in 214 show a large quadrupole splitting (QS) down to 120 K followed by an onset of a magnetic interaction reaching a saturation internal field of Heff=8.7(5) kOe at T=30 K. From the combined magnetic-quadrupole interaction the angle θ formed by qzz and Heff, the η-parameter, and the sign of QS were deduced and information on the local spin structure is derived. Studies conducted with the 123 material (Tc=90 K) reveal a broad unsplit line at temperatures down to 60 K followed by an abrupt onset of a magnetic interaction corresponding to Heff (Sn)=8.3(1) kOe. The hyperfine field decreases with decreasing temperature reaching 6.0(1) kOe at 16 K. The onset of the magnetic interaction at the 119Sn nucleus is explained as due to a local depletion of holes following the Sn4+ doping and a consequent quenching of the magnetic fluctuations in its vicinity. (orig.)