Temperature And Concentration-Dependent Relaxation Of Ferrofluids Characterized With A High-T-C Squid-Based Nuclear Magnetic Resonance Spectrometer

We investigated the relaxation of protons in magnetic fluids using a high-T-c SQUID magnetometer. It was found that the longitudinal relaxation rate, 1/T-1, is slower than the transverse relaxation rate, 1/T-2, for ferrofluids in the same field. This is due to the fact that the 1/T-1 process involves returning the magnetization to the z-direction, which automatically involves the loss of magnetization in the x-y plane governed by the 1/T-2 process. Additionally, 1/T-1 and 1/T-2 at high temperatures are slower than the corresponding relaxation rates at low temperatures, which is due to the enhanced Brownian motion of nanoparticles at high temperatures. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4718032]