Evidence of ferromagnetic short-range correlations in cubic La1-xSrxMnO3-{\delta} (x=0.80, 0.85) above antiferromagnetic ordering

TL;DR

This study reveals persistent ferromagnetic short-range correlations in cubic La1-xSrxMnO3-{eta} above the antiferromagnetic transition temperature, indicating complex magnetic interactions influenced by chemical disorder and oxygen stoichiometry.

Contribution

It provides the first evidence of robust ferromagnetic correlations persisting well above TN in cubic La1-xSrxMnO3-{eta}, highlighting their role in colossal magnetoresistance phenomena.

Findings

Ferromagnetic correlations exist up to 365 K, above TN.

Short-range FMC survive under high magnetic fields, indicating robustness.

Oxygen off-stoichiometry has minimal effect on FMC nature and strength.

Abstract

We report the existence of ferromagnetic correlations (FMC) in paramagnetic (PM) matrix of cubic La1-xSrxMnO3-{\delta} (x = 0.80, 0.85) well above its coupled structural, magnetic and electronic phase transitions. The dc-magnetization vs temperature [M(T)] behaviour under different magnetic fields (from 100 Oe to 70 kOe) shows the presence of short range magnetic correlations up to (TFMC ~) 365 K, far above the antiferromagnetic ordering temperatures (TN =) 260 K and 238 K for x=0.80 and 0.85, respectively. More importantly the observed short-range FMC survive even up to 70 kOe, which indicates their robust nature. The temperature region between TN to TFMC is dominated by the presence of correlated ferromagnetic (FM) entities within the PM matrix and stabilized due to A-site chemical disorder. Our results further illustrate that for the studied compositions, the oxygen off-stoichiometry does not have any significant effect on the nature and strength of these FM entities; however, FM interactions increase in the oxygen deficient samples. These compositions are the unique examples, where the presence of FMC is observed in an undistorted basic cubic perovskite lattice well above TN and therefore are novel to understand the physics behind the colossal magneto-resistance effect.