Magnetic properties of PrBa sub(2)Cu sub(2)MO sub(8-y)(M = Ta, Nb)

• Published in: Solid state communications 1993-01, Vol.85 (2), p.105-109
• Main Authors: Jhans, H, Malik, S K, Vijayaraghavan, R
• Format: Article
• Language: English
• ISSN: 0038-1098

We have investigated the magnetic properties of PrBa sub(2)Cu sub(2)MO sub(8-y) (PrBCMO) (M = Ta, Nb), in which MO sub(6) octahedra replace the square planar Cu in the parent compound, PrBa sub(2)Cu sub(3)O sub(7-y) (PrBCO). Signature of an antiferromagnetic (AFM) transition at 9 K for Pr sub(1.1)Ba sub(1.9)Cu sub(2.1)Ta sub(0.9)O sub(8-y) (Pr sub(1.1)BCTO) and at 10 K for PrBa sub(2)Cu sub(2)NbO sub(8-y) (PrBCNO) is found in the magnetic susceptibility versus temperature curve. The value for the latter is somewhat lower than that observed recently. The transition temperatures are approximately half the value of 17 K observed for PrBCO. This transition in the absence Cu(1)-O(1) chains in PrBCMO means that it is due to the Pr sublattice ordering as confirmed recently. Our results also imply that the copper chains are not required for the ordering of the Pr sublattice. However, a reduction in T sub(N) indicates that the Cu(1)-O(1) chains, acting as separator layers between the CuO sub(2) planes, may play a role. The effect of separator layers, Cu(1)-O(1)/MO sub(6), on the Pr-containing block, CuO sub(2)-Pr-CuO sub(2), is to change the double-layer CuO sub(2) spacing, which in turn may control T sub(N) through hybridization effects. The Neel point seems to be related to this CuO sub(2) interlayer spacing in Pr-based cuprates. The effective paramagnetic moment of the Pr ion is found to be 3.06 mu sub(B) and 2.85 mu sub(B), respectively, for Pr sub(1.1)BCTO and PrBCNO, a value somewhat higher than that found for PrBCO.