Robust paramagnetism in Bi2-xMxRu2O7 (M=Mn,Fe,Co,Ni,Cu) pyrochlore

TL;DR

This study investigates the magnetic, electrical, and thermoelectric properties of Bi2-xMxRu2O7 pyrochlores with various transition metal dopants, revealing diverse magnetic behaviors and metallic states depending on the dopant type.

Contribution

It provides the first comprehensive characterization of magnetic and electronic properties across different transition metal dopants in Bi2-xMxRu2O7 pyrochlores, highlighting the independence of Ru-O and Bi-O sublattices.

Findings

No ferromagnetism observed in doped samples.

Cobalt induces localized Co2+ moments and spin-glass behavior.

Copper enhances the metallic density of states.

Abstract

We report physical property characterization of Bi2-xMxRu2O7 pyrochlores, including magnetic suseptibility, resistivity, and Seebeck coefficients. The solid solution exists up to x=0.5 for (M=Cu,Ni,Co) and up to x=0.1 for (M=Fe,Mn). None of the doped materials exhibit ferromagnetism or any localized ruthenium moment behavior. Instead we find the Ru-O and Bi-O sublattices to be essentially independent, with any magnetism resulting from the unpaired transition metal dopant spins. Cobalt substitution for bismuth results in localized Co{2+}, and low temperature spin-glass transitions in several cases. Nickel moments on the pyrochlore lattice display properties intermediate to localized and itinerant. Finally, copper doping results in only an enhancement of the Pauli metallic density of states.