Decrease in the crystallite diameter of solid crystalline magnetite around the curie temperature by microwave magnetic fields irradiation

Takayuki Tsuchida, Jun Fukushima, Hirotsugu Takizawa

Research output: Contribution to journalArticlepeer-review

Abstract

A decrease in the crystallite diameter of ferrites irradiated with microwaves has been considered as a non-thermal effect of so-called de-crystallization; however, its mechanism has not been elucidated. We hypothesized that a decrease in the crystallite diameter is caused by interaction between the ordered spins of ferrite and the magnetic field of microwaves. To verify this, we focused on magnetite with a Curie temperature of 585C. Temperature dependence around this temperature and time dependence of the crystallite diameter of the magnetite irradiated with microwaves at different temperatures and durations were investigated. From the X-ray diffraction data, the crystallite diameter of magnetite exhibited a minimum value at 500C, just below the Curie temperature of magnetite, where the energy loss of the interaction between magnetite’s spins and the microwaves takes the maximum value. The crystallite diameter exhibited a minimum value at 5 min irradiation time, during which the microwaves were excessively absorbed. Transmission electron microscopy observations showed that the microstructure of irradiated magnetite in this study was different from that reported previously, indicating that a decrease in the crystallite diameter is not caused by de-crystallization but its similar phenomenon. A decrease in coercivity and lowering temperature of Verwey transition were observed, evidencing decreased crystallite diameter. This study can thus contribute to the development of the theory of a non-thermal effect.

Original languageEnglish
Article number984
JournalNanomaterials
Volume11
Issue number4
DOIs
Publication statusPublished - 2021 Apr

Keywords

  • Curie temperature
  • De-crystallization
  • Ferrites
  • Magnetite
  • Microwave processing
  • Non-thermal effects

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Science(all)

Fingerprint Dive into the research topics of 'Decrease in the crystallite diameter of solid crystalline magnetite around the curie temperature by microwave magnetic fields irradiation'. Together they form a unique fingerprint.

Cite this