Eur. Phys. J. B 57, 1-7 (2007)
https://doi.org/10.1140/epjb/e2007-00149-8

Magnetotransport of lanthanum doped RuSr₂GdCu₂O₈ – the role of gadolinium

¹ Department of Physics, Faculty of Science, University of Zagreb, P.O. Box 331, 10002 Zagreb, Croatia
² 2. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany
³ Industrial Research, P.O. Box 31310, Lower Hutt, New Zealand

Corresponding author: ^a mpozek@phy.hr

Received: 20 December 2006
Revised: 27 April 2007
Published online: 25 May 2007

Abstract

Strongly underdoped RuSr_1.9La_0.1GdCu₂O₈ has been comprehensively studied by dc magnetization, microwave measurements, magnetoresistivity and Hall resistivity in fields up to 9 T and temperatures down to 1.75 K. Electron doping by La reduces the hole concentration in the CuO₂ planes and completely suppresses superconductivity. Microwave absorption, dc resistivity and ordinary Hall effect data indicate that the carrier concentration is reduced and a semiconductor-like temperature dependence is observed. Two magnetic ordering transitions are observed. The ruthenium sublattice orders antiferromagnetically at 155 K in low applied magnetic fields, and the gadolinium sublattice orders antiferromagnetically at 2.8 K. The magnetoresistivity in this compound exhibits a complicated temperature dependence due to the occurence of the two magnetic orders and spin fluctuations. It is shown that the ruthenium magnetism influences the conductivity in the RuO₂ layers while the gadolinium magnetism influences the conductivity in the CuO₂ layers. The magnetoresistivity is isotropic above 4 K, but it becomes anisotropic close to the gadolinium antiferromagnetic order temperature.