Korringa-like relaxation in the high-temperature phase of A-site ordered YBaMn2O6

TL;DR

This study reveals a Korringa-like spin relaxation in high-temperature A-site ordered YBaMn2O6, indicating a truly metallic phase with unconventional properties, contrasting with disordered samples.

Contribution

It demonstrates the presence of Korringa-like relaxation in the high-temperature phase of A-site ordered YBaMn2O6, a novel observation in manganites.

Findings

Korringa-like relaxation observed above charge-ordering transition

High-temperature phase exhibits metallic behavior

Disordered samples show spin-spin relaxation typical of manganites

Abstract

We report on high-temperature electron spin resonance studies of A-site ordered YBaMn2O6 and disordered Y0.5Ba0.5MnO3. In the disordered sample we find that the linewidth is governed by spin-spin relaxation processes as in many other manganite systems. In contrast we find a Korringa-like spin relaxation with a slope of about 1 Oe/K above the charge-ordering transition and extending up to 930K in the metal ordered YBaMn2O6 samples. A Korringa-law is a clear feature of a truly metallic state, pointing to an unconventional high-temperature phase of these ordered manganites. In agreement with the ESR intensity this suggests that in the metallic high-temperature phase the ESR signal stems from Mn^4+ core spins which relax via the quasi-delocalized e_g electrons.