Complex room temperature ferrimagnetism induced by zigzag oxygen-vacancy stripes in Sr3YCo4O10.72

TL;DR

This study reveals that oxygen vacancy ordering in Sr3YCo4O10+delta creates zigzag stripes that induce complex ferrimagnetism at room temperature, explained by a collinear G-type magnetic structure with distinct Co spin states.

Contribution

It provides the first detailed structural and magnetic model linking oxygen vacancy patterns to ferrimagnetism in Sr3YCo4O10+delta, clarifying the origin of high-temperature ferromagnetism.

Findings

Oxygen vacancy ordering forms zigzag stripes in CoO4+delta layers.

A collinear G-type magnetic structure with uncompensated moments is proposed.

Calculated magnetic moments match bulk magnetization data.

Abstract

The high temperature ferromagnetism in Sr3YCo4O10+delta perovskite, whose origin has been the subject of a considerable debate, has been studied by neutron powder diffraction and synchrotron X-ray diffraction measurements. Oxygen vacancy ordering creates a complex pattern of zigzag stripes in the oxygen-deficient CoO4+delta layers, where the Co ions are found in three distinct coordinations. The symmetry of this unprecedented structural modulation, in conjunction with the existence of different Co spin states, provide a straightforward explanation for the appearance of ferrimagnetism. A model for the magnetic structure compatible with these structural features is proposed, based on the refinement of powder neutron data. The macroscopic moment as a function of temperature that can be calculated from the values of the ordered spins extracted from refinements, is in excellent agreement with bulk magnetization. Unlike previous models, a collinear G-type magnetic structure with uncompensated moments due to distinct spin-states of Co imposed by different coordination is found.