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.