Spin-spin relaxation of protons in ferrofluids characterized with a high-T c superconducting quantum interference device-detected magnetometer in microtesla fields

Shu Hsien Liao, Chieh Wen Liu, Hong Chang Yang, Hsin Hsien Chen, Ming Jye Chen, Kuen Lin Chen, Herng Er Horng, Li Min Wang, Shieh Yueh Yang

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In this work, the spin-spin relaxation of protons in ferrofluids is characterized using a high-T c SQUID-based detector in microtesla fields. We found that spin-spin relaxation rate is enhanced in the presence of superparamagnetic nanoparticles. The enhanced relaxation rates are attributed to the microscopic field gradients from magnetic nanoparticles that dephase protons' spins nearby. The relaxation rates decrease when temperatures increase. Additionally, the alternating current magnetic susceptibility was inversely proportional to temperature. Those characteristics explained the enhanced Brownian motion of nanoparticles at high temperatures. Characterizing the relaxation will be helpful for assaying bio-molecules and magnetic resonance imaging in microtesla fields.

Original languageEnglish
Article number232405
JournalApplied Physics Letters
Issue number23
Publication statusPublished - 2012 Jun 4


ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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