Oxygen hyperstoichiometric hexagonal ferrite CaBaFe4O7+\delta (\delta \approx 0.14) : coexistence of ferrimagnetism and spin glass behavior

TL;DR

This study synthesizes an oxygen-rich hexagonal ferrite CaBaFe4O7+b4, revealing coexistence of ferrimagnetism and spin glass behavior due to cationic disordering, with notable magnetic frustration and complex phase crossover phenomena.

Contribution

It introduces a new oxygen hyperstoichiometric ferrite with altered magnetic properties and analyzes the coexistence of ferrimagnetism and spin glass behavior caused by cationic disordering.

Findings

High Curie temperature of 270 K maintained

Weakening of ferrimagnetism with increased oxygen content

Observation of spin glass transition at 166 K

Abstract

An oxygen hyperstoichiometric ferrite CaBaFe4O7+\delta (\delta \approx 0.14) has been synthesized using "soft" reduction of CaBaFe4O8. Like the oxygen stoichiometric ferrimagnet CaBaFe4O7, this oxide also keeps the hexagonal symmetry (space group: P63mc), and exhibits the same high Curie temperature of 270 K. However, the introduction of extra oxygen into the system weakens the ferrimagnetic interaction significantly at the cost of increased magnetic frustration at low temperature. Moreover, this canonical spin glass (Tg ~ 166 K) exhibits an intriguing cross-over from de Almeida-Thouless type to Gabay-Toulouse type critical line in the field temperature plane above a certain field strength, which can be identified as the anisotropy field. Domain wall pinning is also observed below 110 K. These results are interpreted on the basis of cationic disordering on the iron sites.