The structure, Curie temperature and magnetostriction of PrxDy1−xFe2 (0⩽x⩽0.5) and Pr0.4Dy0.6(Fe1−yMy)2 (0⩽y⩽0.6) alloys (M=Co, Ni) have been investigated using optical microscopy, x-ray diffraction, ac initial susceptibility and standard strain gauge techniques. The matrix of homogenized PrxDy1−xFe2 alloys is a cubic Laves phase (Pr, Dy)Fe2 with MgCu2-type structure, with a small amount of second phase (Pr, Dy)Fe3 when x⩽0.2. The amount of (Pr, Dy)Fe3 phase increases with the increase of Pr content, and it becomes the main phase when x=0.4. When x=0.5, the matrix is found to be the (Pr, Dy)2Fe17 phase coexisting with a small amount of phases (Pr, Dy)Fe2, (Pr, Dy)Fe3 and rare-earth rich phases. For Pr0.4Dy0.6(Fe1−yCoy)2 alloys, the amount of (Pr, Dy)(Fe, Co)2 phase increases with increasing Co content and the phase (Pr, Dy)(Fe, Co)2 becomes the main phase when y=0.6. However, the substitution of Ni for Fe up to 60 at % Ni in Pr0.4Dy0.6Fe2 alloys does not favor the formation of the cubic Laves phase (Pr, Dy)(Fe, Ni)2. The lattice constant of PrxDy1−xFe2 alloys decreases with increasing x, whereas the Curie temperature Tc increases. The magnetostriction of PrxDy1−xFe2 alloys at room temperature exhibits a peak at x=0.3. The lattice constant of Dy0.6Pr0.4(Fe1−yCoy)2 alloys decreases slowly with increasing y; Tc shows a peak when y=0.45, and the room temperature magnetostriction becomes negative when x>0.45. The Curie temperature of Dy0.6Pr0.4(Fe1−yNiy)2 alloys decreses with the increase of Ni content. The room temperature magnetostriction of Dy0.6Pr0.4(Fe1−yNiy)2 also becomes negative when x>0.45.
The dependence of coupling coefficient (k) and elastic moduli (EH and EB) on particle size and volume fraction of Terfenol powder in polymer-bonded composites has been investigated. Materials were prepared with powder in five size ranges between 106 and 710 μm and in three volume fractions (VF). The moduli show a ΔE effect, which is negative for small bias fields and positive for larger fields. EH is found to be independent of particle size and to vary with VF in agreement with model predictions. The maximum value of k, for each sample, is found to be independent of both particle size and VF and a simple model is presented which predicts this behavior and indicates that the low values of kmax arise mainly from the low modulus of the epoxy binder.
The magnetostriction and magnetization process of a twin-free Tb0.27Dy0.73Fe2 single crystal along the 〈110〉 direction has been studied by strain gauge, vibrating sample magnetometer, and domain observation techniques. It was observed that the magnetostriction of the sample remained unchanged with increasing magnetic fields when H<1 kOe and quickly increased in the range 1<H<7.5 kOe. No “jump” effect was observed during the magnetization process and the magnetostrictive hysteresis was large when H<2.5 kOe. Observations by the Bitter colloid technique at room temperature revealed curved domain walls which became straight at higher and lower temperatures in {100} and {111}, respectively, indicating the transition to different 180° walls for H<1 kOe. The domain patterns were clearest on a {100} surface. Above the spin reorientation temperature, 109° and 71° wall motions dominated the magnetization process in the range 1.5 kOe<H<4 kOe, but below it, clear 90° wall motions were observed. Little change in the magnetized domain pattern was observed at different temperatures suggesting that many domain walls occupy the same planes. Similar room temperature patterns were observed at remanence with an applied stress along 〈111〉 in excess of 5 MPa. These results are consistent with theoretical magnetomechanical behavior based on a 〈1uu〉, 0<u<1, transition in easy direction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.