Magnetic interactions in119Sn substituted for Cu in antiferromagnetic and superconducting lamellar cuprates

Abstract

Mossbauer Spectroscopy (MS) studies of119Sn 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 diffusing119SnO2 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 ofHeff=8.7(5) kOe atT=30K. From the combined magnetic-quadrupole interaction the angle θ formed byqzz andHeff, the η-parameter, and the sign ofQS 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 toHeff (Sn)=8.3(1) kOe. The hyperfine fielddecreases with decreasing temperature reaching 6.0(1) kOe at 16 K. The onset of the magnetic interaction at the119Sn 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.