Influence of size distribution and field amplitude on specific loss power

摘要

Herein we present the results of specific loss power (SLP) analysis of polydisperse water based ferrofluids, Fe_3O_4/PEG200 and Fe_3O_4/PEG6000, with average Fe_3O_4 particle size of 9 nm and 11 nm, respectively. Specific loss power was measured in alternating magnetic field of various amplitudes and at fixed frequency of 580.5 kHz. Maximum SLP values acquired were 195 W/g for Fe_3O_4/PEG200 and 60 W/g for Fe_3O_4/PEG6000 samples. The samples were labeled as superparamagnetic by magnetization measurements, but SLP field dependence showed deviation from the behavior predicted by the commonly employed linear response theory. The scope of this theory for both samples with wide particle size distribution is discussed. Deviation from the expected behavior is explained by referring to polydisperse nature of the samples and field dependent relaxation rates.