Magnetization and magnetoresistance in insulating phases of SrFeO3-d

TL;DR

This study investigates two new insulating phases of SrFeO3-d with oxygen deficiencies, revealing complex magnetic behaviors, magnetoresistance effects, and magnetic frustration related to Fe oxidation states.

Contribution

It introduces and characterizes two novel insulating SrFeO3-d phases with distinct magnetic and transport properties due to oxygen deficiency.

Findings

Sample A exhibits large negative magnetoresistance near charge ordering temperature.

Sample B shows smooth insulating behavior with small positive magnetoresistance.

Multiple magnetic features indicate frustrated helical magnetic order.

Abstract

We report the synthesis and properties of two new insulating phases of SrFeO3-d with introduction of oxygen deficiencies in metallic SrFeO3 ; one with 0.15 < d < 0.19 (sample A)and the other above d = 0.19 (sample B). Sample A shows large negative magnetoresistance around the charged ordering (CO) temperature with magnetic anomalies seen in the temperature dependent resistivity,magnetization and M-H hysteresis loops. Sample B shows a smooth insulating behavior with no thermal hysteresis in the resistivity and with a small positive magnetoresistance. cac and cdc show multiple features associated with a frustrated magnetic order (helical) due to competing ferro- and antiferromagnetic interactions. The competing effects of ferro- and antiferromagnetic phases extend up to T ~ 230 K revealing a new high temperature scale in this system. These observations are discussed in the context of magnetic interactions associated with the varying Fe4+/Fe3+ ratio.