Major and minor stress-magnetization loops in textured polycrystalline Fe81.6Ga18.4 Galfenol

Abstract

Major and minor magnetization versus stress loops under different bias magnetic fields from 0.8 kA/m to 8.0 kA/m in 0.8 kA/m steps were measured in research grade, ⟨100⟩ oriented, textured polycrystalline Fe81.6Ga18.4. Both compressive and tensile stresses were applied from −63 MPa to 63 MPa for major loop analysis. Minor loops were generated by superimposing a 4.0 Hz, 2.8 MPa amplitude sinusoidal stress on different dc compressive stresses ranging from −40.7 MPa to −5.6 MPa in 7.0 MPa increments. Bias magnetic fields were applied in two ways, constant field in the sample obtained using a controller and constant current to the excitation coils. An energy-averaged model and related optimization method are presented to compare the experiments with simulations. The slope of magnetic flux density versus stress, i.e., the material's sensitivity to stress, is quantified from major and minor loop measurements. The peak sensitivity at constant field is about 75 T/GPa for constant-field major loops, whereas it is 41 T/GPa for constant-current major loops. The sensitivity for minor loops is consistently lower than for major loops, whether at constant field or constant current.