Magnetotransport of lanthanum doped RuSr2GdCu2O8 - the role of gadolinium

TL;DR

This study investigates how lanthanum doping affects the magnetic and electronic properties of RuSr2GdCu2O8, revealing complex magnetic ordering and the influence of gadolinium on conductivity and magnetoresistivity.

Contribution

It provides a comprehensive analysis of magnetic transitions and magnetotransport in La-doped RuSr2GdCu2O8, highlighting the roles of ruthenium and gadolinium sublattices.

Findings

La doping suppresses superconductivity and reduces carrier concentration.

Two magnetic transitions at 155 K (Ru) and 2.8 K (Gd) are observed.

Gadolinium magnetism affects conductivity and magnetoresistivity anisotropy.

Abstract

Strongly underdoped RuSr_1.9La_0.1GdCu_2O_8 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 for low applied magnetic field and the gadolinium sublattice antiferromagnetically orders at 2.8 K. The magnetoresistivity exhibits a complicated temperature dependence due to the combination of the two magnetic orderings 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 when gadolinium orders antiferromagnetically.