Role of shell thickness and applied field on the magnetic anisotropy and temperature dependence of coercivity in Fe3O4/γ-Fe2O3 core/shell nanoparticles

Chiranjib Nayek, M. Ali Al-Akhras, Venkatesha Narayanaswamy, Abbas Khaleel, Imaddin A. Al-Omari, Andrivo Rusydi, Ihab M. Obaidat*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

We report on the effect of shell thickness and the agnetic field on the effective agnetic anisotropy, Keff and on the teperature dependence of coercivity, HC(T) inFe3O4/γ-Fe2O3 core/shell nanoparticles of fixed diaeter (8 n) and several shell thicknesses (1, 3 and 5 n). The particles are synthesized by the usual co-precipitation ethod. The phase and the orphology of the saple are characterized by X-ray diffraction and transission electron icroscopy. The orphology of the nanoparticles is confired by high resolution transission electron icroscopy (HRTEM) and selected area electron diffraction (SAED). The agnetic easureents are carried out using a SQUID in the teperature range of 2 K to 300 K both under zero field-cooling (ZFC) and field-cooling (FC) protocols with field-cooling values, HFC of 0.5 T, 1 T, 2 T and 3 T. HC(T) in the saples is found to significantly deviate fro the original Kneller’s law. These deviations are attributed to odifications of the interfacial agnetic anisotropy that resulted fro variations in the interfacial spin-glass regions with shell thickness and field-cooling. Keff is calculated using two ethods based on the agnetization easureents. In the first ethod we used the HC(T) curves obtained fro the ZFC and FC agnetization versus agnetic field M–H hysteresis loops. In the second ethod the ZFC agnetization versus teperature (M–T) easureents are used at several applied agnetic fields. We copared and discussed the different results of Keff obtained by these two methods.

Original languageEnglish
Pages (from-to)123-132
Number of pages10
JournalMaterials Express
Volume9
Issue number2
DOIs
Publication statusPublished - 2019

Keywords

  • Anisotropy
  • Coercivity
  • Kneller’s law
  • Magnetization
  • Nanoparticles

ASJC Scopus subject areas

  • Materials Science(all)

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