Size Dependence of the Magnetoelastic Properties of Metallic Glasses for Actuation Applications.

We present an exhaustive study of the magnetoelastic properties of 24 strips with different rectangular dimensions, cut from a long ribbon of Metglas 2826MB3. The strips have a length-to-width ratio ranging from 2 to over 20. Significant variations of the apparent saturation Young's modulus and the effect with strip geometry, changing from 160 GPa and 4% for = 10 mm, = 5 mm and = 2, to 164 GPa and 9.6% for = 35 mm, = 1.7 mm and = 20.6, have been observed. In order to obtain the highest values of the effect, the magnetomechanical coupling coefficient, , and the quality factor of the resonance, , a value > 14 is needed. The effective anisotropy field , taken as the minimum of the curve, and its width , are not as strongly influenced by the value, and a value of > 7 is enough to reach the lowest value. From our measurements we infer that the formerly predicted value of > 5 needed for a good magnetic and magnetoelastic response of the material must be actually regarded as the lowest limit for this parameter. In fact, we show that the demagnetizing factor , rather than the length-to-width ratio , is the parameter that governs the magnetoelastic performance of these strips.