Magnetism and compressive modulus of magnetic fluid containing gels

We have investigated the magnetism and have measured the compressive modulu s of magnetic fluid containing gels, called ferrogels, in the presence of m agnetic field. No hysteresis was shown in the magnetization curve of the fe rrogel suggesting a super paramagnetic response. The equilibrium compressiv e modulus of the ferrogel was measured up to 4 kOe and the modulus with fie ld was much higher than that without field. The mean change in modulus incr eased with increasing magnetic field, and it saturates above 2 kOe. The mea n and maximum change in modulus at 4 kOe was 31 and 71 Pa which corresponds to 19% and 46% increases of that without field, respectively. The change i n modulus has been analyzed theoretically and is well explained in terms of the magnetism of ferrogels. (C) 1999 American Institute of Physics. [S0021 -8979(99)03612-9].