High-field magnetization and magnetoresistance of the $A$-site ordered perovskite oxide CaCu$_{3}$Ti$_{4-x}$Ru$_{x}$O$_{12}$~($0 \le x \le 4$)

TL;DR

This study investigates the magnetic and magnetoresistive properties of CaCu3Ti4-xRuxO12, revealing nonlinear magnetization behavior at intermediate Ru concentrations and significant magnetoresistance, linked to hole delocalization on Cu2+ ions.

Contribution

It provides new insights into the magnetic field effects on A-site ordered perovskite oxides with varying Ru content, highlighting the role of hole delocalization in their magnetic and transport properties.

Findings

Nonlinear magnetization for x=0.5, 1.0, 1.5

Magnetoresistance of -70% at 4.2 K and 52 T for x=1.5

Field-induced hole delocalization on Cu2+ ions

Abstract

We have measured high-field magnetization and magnetoresistance of polycrystalline samples of the A-site ordered perovskite CaCu3Ti4-xRuxO12 (x=0 - 4) utilizing a non-destructive pulsed magnet. We find that the magnetization for x=0.5, 1.0 and 1.5 is nonlinear, and tends to saturate in high fields. This is highly nontrivial because the magnetization for x=0 and 4 is linear in external field up to the highest one. We have analyzed this field dependence based on the thermodynamics of magnetic materials, and propose that the external fields delocalize the holes on the Cu2+ ions in order to maximize the entropy. This scenario is qualitatively consistent with a large magnetoresistance of -70% observed at 4.2 K at 52 T for x=1.5.