Continuous-wave measurements of the shear elastic constants of bcc Fe–Ga solid solutions show that the constant C44 is independent of the gallium composition while the constant 12(C11–C12) decreases linearly and extrapolates to zero at 26 at. % Ga. This result indicates that the Fe–Ga solid solution is inhomogeneous and contains clusters consisting of embryos of a martensitic phase. The increasing softness of 12(C11–C12) then reflects an increase of the embryo density. A model assuming that the clusters are centered around next-nearest Ga pairs reproduces the known composition dependence of the magnetostrictive constant λ100 in the composition range 0<XGa<0.23 with only one adjustable parameter. Its value suggests a cluster size of 12 atoms.

The temperature dependencies of the elastic constants of martensitic Ni0.50Mn0.284Ga0.216 were studied in the temperature range from 428 K down to 200 K. Measurements were conducted using the ultrasonic continuous-wave method in a 0.8 T magnetic field. At 220 K abrupt changes were found in the temperature dependences of the velocities of all 11 elastic wave modes, which indicates a structural phase change from the tetragonal (5M) martensite to a second, probably tetragonal, phase (nonlayered) at lower temperature.

It is known that the substitution of Co for Fe gives rise to increases in magnetization and Curie temperature, not only in the bcc metals, but also in intermetallic compounds and alloys as well. With the expectation that this is the case in Co-substituted FeGa, we measured magnetization, Curie temperature, magnetostriction and elastic constants of a series of polycrystalline FeCoGa ternary alloys with up to 17% Ga and up to 10% Co. The magnetostriction at saturation for Fe 0.93−x Co .07 Ga x increases to 90 ppm for x=0.17. For larger percentages of Co, the rise in magnetostriction is not as sharp as it is in the 7% case. The shear elastic modulus decreases with Ga, again in keeping with the results for FeGa. The magnetostriction and the elastic constants are sensitive to sample preparation for the high-Ga material. We conclude that the substitution of small (<0.10)percentages of Co for Fe in bcc FeCoGa alloys enhances the magnetic and magnetostrictive properties of the parent FeGa material. It is known that the substitution of Co for Fe gives rise to increases in magnetization and Curie temperature, not only in the bcc metals, but also in intermetallic compounds and alloys as well. With the expectation that this is the case in Co-substituted FeGa, we measured magnetization, Curie temperature, magnetostriction and elastic constants of a series of polycrystalline FeCoGa ternary alloys with up to 17% Ga and up to 10% Co. The magnetostriction at saturation for Fe 0.93Ϫx Co .07 Ga x increases to 90 ppm for xϭ0.17. For larger percentages of Co, the rise in magnetostriction is not as sharp as it is in the 7% case. The shear elastic modulus decreases with Ga, again in keeping with the results for FeGa. The magnetostriction and the elastic constants are sensitive to sample preparation for the high-Ga material. We conclude that the substitution of small (Ͻ0.10) percentages of Co for Fe in bcc FeCoGa alloys enhances the magnetic and magnetostrictive properties of the parent FeGa material.

The temperature dependences of the elastic constants of Ni 0.50 Mn 0.284 Ga 0.216 and Fe 3 Pd were studied. Measurements were conducted by the ultrasonic continuous wave method. Anomalous behavior of the elastic constants temperature dependence in austenitic NiMnGa was observed, especially an abrupt 15% softening of C 11 at the Curie temperature. The latter anomaly was found to be strongly influenced by the presence and orientation of applied magnetic fields. In martensitic NiMnGa, the temperature dependences of the velocities of all eleven elastic wave modes had abrupt changes at 220K, which indicate a structural phase change from the tetragonal to a second phase at lower temperature. The temperature and magnetic field effects in Fe 3 Pd were also studied by the elastic constants measurements.

A near-field room temperature scanning magnetic probe microscope has been developed using a laminated magnetoelectric sensor. The simple trilayer longitudinal-transverse mode sensor, fabricated using Metglas as the magnetostrictive layer and polyvinylidene fluoride as the piezoelectric layer, shows an ac field sensitivity of 467±3μV∕Oe in the measured frequency range of 200Hz–8kHz. The microscope was used to image a 2mm diameter ring carrying an ac current as low as 10−5A. ac fields as small as 3×10−10T have been detected.