Effect of Dipole Interactions on Blocking Temperature and Relaxation Dynamics of Superparamagnetic Iron-Oxide (Fe3O4) Nanoparticle Systems

Md Ehsan Sadat; Sergey L Bud'ko; Rodney C Ewing; Hong Xu; Giovanni M Pauletti; David B Mast; Donglu Shi

doi:10.3390/ma16020496

Effect of Dipole Interactions on Blocking Temperature and Relaxation Dynamics of Superparamagnetic Iron-Oxide (Fe₃O₄) Nanoparticle Systems

Materials (Basel). 2023 Jan 4;16(2):496. doi: 10.3390/ma16020496.

Authors

Md Ehsan Sadat¹, Sergey L Bud'ko², Rodney C Ewing³, Hong Xu⁴, Giovanni M Pauletti⁵, David B Mast¹, Donglu Shi⁶

Affiliations

¹ Department of Physics, University of Cincinnati, Cincinnati, OH 45221, USA.
² Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA.
³ Department of Geological Sciences, Stanford University, Stanford, CA 94305-2115, USA.
⁴ Med-X Institute, Shanghai Jiao Tong University, Shanghai 200030, China.
⁵ Department of Pharmaceutical and Administrative Sciences, St. Louis College of Pharmacy, University of Health Sciences & Pharmacy, St. Louis, MO 63110, USA.
⁶ The Materials Science and Engineering Program, Department of Mechanical and Materials Engineering, College of Engineering and Applied Science, University of Cincinnati, Cincinnati, OH 45221, USA.

Abstract

The effects of dipole interactions on magnetic nanoparticle magnetization and relaxation dynamics were investigated using five nanoparticle (NP) systems with different surfactants, carrier liquids, size distributions, inter-particle spacing, and NP confinement. Dipole interactions were found to play a crucial role in modifying the blocking temperature behavior of the superparamagnetic nanoparticles, where stronger interactions were found to increase the blocking temperatures. Consequently, the blocking temperature of a densely packed nanoparticle system with stronger dipolar interactions was found to be substantially higher than those of the discrete nanoparticle systems. The frequencies of the dominant relaxation mechanisms were determined by magnetic susceptibility measurements in the frequency range of 100 Hz-7 GHz. The loss mechanisms were identified in terms of Brownian relaxation (1 kHz-10 kHz) and gyromagnetic resonance of Fe₃O₄ (~1.12 GHz). It was observed that the microwave absorption of the Fe₃O₄ nanoparticles depend on the local environment surrounding the NPs, as well as the long-range dipole-dipole interactions. These significant findings will be profoundly important in magnetic hyperthermia medical therapeutics and energy applications.

Keywords: Fe3O4 nanoparticles; blocking temperature; gyromagnetic resonance; magnetic relaxation.

Grants and funding

This research was funded by National Science Foundation under grant number 1953009 (DS) and the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358 (SLB).