  It is shown that in external magnetic fields, a uniaxial magnetic anisotropy
comes into being in a magnetoactive elastomer (MAE). The magnitude of the
induced uniaxial anisotropy grows with the increasing external magnetic field.
The filler particles are immobilized in the matrix if the MAE sample is cooled
below 220 K, where the anisotropy can be read out. The cooling of the sample is
considered as an alternative methodological approach to the experimental
investigation of the magnetized state of MAEs. The appearance of magnetic
anisotropy in MAE is associated with restructuring of the filler during
magnetization, which leads to an additional effective field felt by the
magnetization. It is found that the magnitude of the effective magnetic
anisotropy constant of the MAE is approximately two times larger than its
effective shear modulus in the absence of magnetic field. It is proposed that
the experimentally observed large (about 40) ratio of the magnetic anisotropy
constant of the filler to the shear modulus of the matrix deserves attention
for the explanation of magnetic and magnetoelastic properties of MAEs. It may
lead to additional rigidity of the elastic subsystem increasing the shear
modulus of the composite material through the magnetomechanical coupling.
