Low temperature FMR investigations on double surfactant water based ferrofluid

Ajay Shankar, Mahesh Chand, Gounda Abdul Basheed, Sanjeeve Thakur, Rajendra Prasad Pant

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

Magnetite nanoparticles were synthesized by coprecipitation of reverse micelles in an aqueous phase. XRD, TEM and VSM results confirm the average particle size 9-10 nm. The FMR measurements were performed in zero-field-cooled (ZFC) and field-cooled (FC) protocol. Raikher and Morais models were used for interpreting the resonance field and linewidth results. A value of 2.3×10-2erg cm-2for intrinsic surface anisotropy constant is observed as per the Raikher model. The higher melting point of water leaves the magnetic particles with a more disordered distribution of anisotropy axes of particles even in FC measurements. The angular variation of resonance field differentiates the magnetic behavior of system in 4-40 K (region I), 70-200 K (region II) and 200-260 K (region III). The value of effective magnetic anisotropy constant varied from 4.7×104, 2.1×104to 0 erg cm-3through regions I, II to III. Linewidth analysis reveals that system undergoes spin-glass transition ~46 K. The fitting of linewidth data for region I and II indicate the presence of frozen and unfrozen surface spin states. Moreover, the role of applied magnetic field i.e. 1 T in field-cooled FMR spectra is reflected in interparticle distance parameter and magnitude of energy barriers related to the relaxation mechanisms. At 260 K fluid melts resulting in minimization of angular dependent anisotropy in resonance lines.

Original languageEnglish
Pages (from-to)696-702
Number of pages7
JournalJournal of Magnetism and Magnetic Materials
Volume374
DOIs
Publication statusPublished - 15 Jan 2015
Externally publishedYes

Keywords

  • Ferrofluid
  • Ferromagnetic resonance
  • Spin-glass transition

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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