Metal-insulator transition induced by 16O -18O oxygen isotope exchange in colossal negative magnetoresistance manganites

TL;DR

This study demonstrates that oxygen isotope exchange in manganites can induce a reversible metal-insulator transition, significantly affecting magnetic and electronic properties due to changes in electron bandwidth.

Contribution

It reveals a novel isotope-induced metal-insulator transition in manganites, highlighting the role of oxygen isotopes in tuning phase behavior.

Findings

Isotope exchange causes reversible transition from ferromagnetic metal to charge-ordered insulator.

Magnetic field can revert 18O samples back to metallic state, increasing Tc.

Isotope shift of Tc reaches up to 63 K at 2 T.

Abstract

The effect of 16O-18O isotope exchange on the electric resistivity was studied for (La(1-y)Pr(y))0.7Ca0.3MnO3 ceramic samples. Depending on y, this mixed perovskite exhibited different types of low-temperature behavior ranging from ferromagnetic metal (FM) to charge ordered (CO) antiferromagnetic insulator. It was found that at y=0.75, the substitution of 16O by 18O results in the reversible transition from a FM to a CO insulator at zero magnetic field. The applied magnetic field (H >= 2 T) transformed the sample with 18O again to the metallic state and caused the increase in the FM transition temperature Tc of the 16O sample. As a result, the isotope shift of Tc at H = 2 T was as high as 63 K. Such unique sensitivity of the system to oxygen isotope exchange, giving rise even to the metal-insulator transition, is discussed in terms of the isotope dependence of the effective electron bandwidth which shifts the balance between the CO and FM phases.