LaBaNiO4: A Fermi glass

TL;DR

This study investigates LaBaNiO4, revealing it as a Fermi glass with localized electron states despite insulating behavior, challenging traditional classifications of its electronic state.

Contribution

It provides evidence that LaBaNiO4 is a Fermi glass with localized electrons, despite showing insulating transport and metallic-like properties.

Findings

LaBaNiO4 is a Fermi glass with localized electron states.

No magnetic ordering observed down to 1.5 K.

Physical properties resemble metallic LaSrNiO4 despite insulating behavior.

Abstract

Polycrystalline samples of LaSr1-xBaxNiO4 show a crossover from a state with metallic transport properties for x = 0 to an insulating state as x -> 1. The end member LaBaNiO4 with a nominal nickel Ni 3d7 configuration might therefore be regarded as a candidate for an antiferromagnetic insulator. However, we do not observe any magnetic ordering in LaBaNiO4 down to 1.5 K, and despite its insulating transport properties several other physical properties of LaBaNiO4 resemble those of metallic LaSrNiO4. Based on an analysis of electrical and thermal-conductivity data as well as magnetic-susceptibility and low-temperature specific-heat measurements we suggest that LaBaNiO4 is a Fermi glass with a finite electron density of states at the Fermi level but these states are localized.