Adiabatic vs. non-adiabatic determination of specific absorption rate of ferrofluids.
The measurement of temperature variations in adiabatic conditions allows the determination of the specific absorption rate of magnetic nanoparticles and ferrofluids from the correct incremental expression, SAR (1/m(MNP))C(Delta T/Delta t). However, when measurements take place in non-adiabatic conditions, one must approximate this expression by SAR approximate to C beta/m(MNP), where beta is the initial slope of the temperature vs. time curve during alternating field application. The errors arising from the use of this approximation were estimated through several experiments with different isolating conditions, temperature sensors and sample-sensor contacts. It is concluded that small to appreciable errors can appear, which are difficult to infer or control. (c) 2009 Elsevier B.V. All rights reserved.