Synthesis and magnetic properties of the R1+xSr2−xNb1−xO8−y system

✍ Scribed by H. Jhans; S.K. Malik; R. Vijayaraghavan

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 787 KB
• Volume: 215
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(93)90379-5

✦ Synopsis

We have carried out systematic studies involving synthesis of Rj +~Sr2_xCu2+xNbt_xOs_y (x= 0.0-0.2 ), R= La, Pr, Nd, Sm, Eu, Gd, Dy and Y, and have investigated their magnetic properties. For R = La, Dy and Y, the expected RSr2Cu2NbOs_v (RSCNO) phase does not form. For R=Pr and Nd, only an off-stoichiometric composition yields the RSCNO single phase, Prl.2Srt.sCu2.2Nbo.sOs_y (Prt.2SCNO) and Nd~.lSrl.gCuz.lNbo.9Os_y (Nd~.~SCNO), respectively. In contrast, for R = Sm, Eu and Gd, the stoichiometric ratio results in monophasic material. Lattice parameters for Pr~.2SCNO, Nd ~.tSCNO, SmSCNO, EuSCNO and GdSCNO are found to vary linearly with rare earth ionic size. Magnetic susceptibility, Z, for Pr~.2SCNO and GdSCNO, exhibits a magnetic ordering of the R sublattice. This occurs at about 6 K for the former and at about 2.15 K for the latter. The peak in the Z-T curve at 2.15 K for GdSCNO agrees well with the cusp (2.17 K) reported in heat capacity vs. temperature data. The effective paramagnetic moment, #err, for the rare earth ion is deduced to be 2.95/ta in Prt.2SCNO and 7.97,u B in GdSCNO. This result for GdSCNO is consistent with that of heat capacity measurements which indicate an entropy value corresponding to a Gd spin of 3.3. Magnetic susceptibility results do not indicate a magnetic transition down to 1.8 K for the Ndt.tSCNO and SmSCNO compounds. The/leer value is determined to be 3.42/tB for the former. Results on the abovementioned compounds are discussed in the context of the related RBa2Cu2NbOs_y and RBa2Cu307_y systems.