Dependence of ΔEΔE effect on internal stresses in nickel: Experimental results by laser interferometry

The speckle heterodyne interferometry is applied to the study of the dependence of Young's modulus on both the magnetic field and the internal stresses in a soft ferromagnetic material. Young's modulus is determined from the first natural longitudinal frequency of a slender magnetic rod positioned within a solenoid. Vibration of the sample is detected by an optical heterodyne system with a wide bandwidth. The samples are heated to above the Curie point and then cooled at several rates in order to induce different internal stresses. The study refers to nickel rods 10 mm in diameter and 110 mm in length. The grain sizes of the samples are also determined and related to changes in ΔEΔE.