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This paper presents the results of the Villari effect study in FeGa magnetorheological composites with very low stresses. The composites consist of a silicone matrix and Fe75Ga25 powder of size ranging from 50 to 100 µm. Two types of composites, one is with 45 wt% and the other one with 30 wt% of Fe75Ga25 powder have been manufactured. The Villari effect has been measured in both samples as-manufactured and in those in which a 1 T magnetic field has been applied after curing. The results indicate that the composites with an applied field of 1 T after curing show the greatest Villari signal even without any applied magnetic field. This fact allows a design of a low-cost force sensor and high performance. A simple model, based on the change in the cross-section of the composite, has been developed to explain the results obtained.

Magnetic composites of soft magnetic FeGa particles embedded in a silicone matrix have been synthesized. The Villari effect has been studied depending on the size and concentration of the particles and on the magnetic state of the composite. The results indicate a decrease in the Villari effect when the concentration of the magnetic particles increases. These results suggest a relationship between the Villari effect and the mechanical properties of the composites. The Young’s modulus of the composites has been obtained by microindentation and their values related to the intensity and slope of the Villari signals. The results are explained on the basis that the reduction in the cross section of the composite when submitted to stress is the main origin of the variation of the magnetic flux in the Villari effect in this kind of composite. It has also been obtained that the magnetic state of the composite plays an important role in the Villari signal. When the magnetization of the composite is greater, the magnetic flux across the composite is greater too and, so, the same reduction in the cross section originates a greater Villari signal.