$R$-site Randomness Effect in Double-Perovskite $R$BaMn$_{2}$O$_{6}$

TL;DR

This study explores how $R$-site randomness in double-perovskite $R$BaMn$_{2}$O$_{6}$ affects its magnetic and electronic phases, revealing phase separation and magnetoresistance phenomena.

Contribution

It demonstrates the impact of $R$-site randomness on phase transitions and phase separation in $R$BaMn$_{2}$O$_{6}$, a novel insight into disorder effects in these materials.

Findings

$T_{CO}$ decreases with increasing $R$-site randomness.

Strong phase separation occurs among FM, AFM, and COI states.

Large magnetoresistance observed in phase-separated regions.

Abstract

We have investigated the $R$-site randomness effect of $R$/Ba-ordered $R$BaMn$_{2}$O$_{6}$ ($R$ = rare earth) by using Y$_{1-y}$La$_y$BaMn$_2$O$_6$ (0 (\leq) $y$ (\leq) 1) in which $R$ (Y,La) and Ba are regularly arranged while Y and La randomly occupy the $R$-site. YBaMn$_2$O$_6$ ($y$ = 0) undergoes charge/orbital ordering (CO) transition at $T_{\rm CO}$ = 500 K while LaBaMn$_{2}$O$_{6}$ ($y$ = 1) shows ferromagnetic metallic (FM) behavior below 350 K\@. In 0 (\leq) $y$ (\leq) 0.6, $T_{\rm CO}$ decreases with an increase in $y$. In 0.6 (\leq) $y$ (\leq) 0.8, $R$-site randomness causes strong phase separation tendencies among the FM, antiferromagnetic (AFM), and CO insulating (COI) states. The large magnetoresistance is observed in the phase separated region.