Abstract
The magnetostrictive materials are potential for MEMS and device applications, because of their capability to convert magnetic energy to mechanical energy. This thesis reports the magnetostriction and magnetic properties of Tb0.3Dy0.7(Fe,Be)2 bulks, Tb(Fe,Mn,Al)2 bulks, Tb0.3Dy0.7(Fe,Mn,Al)2 ribbons and Tb-Fe thin films. Ingots of Tb0.3Dy0.7(Fe1-xBex)2 (x= 0~0.1) and Tb(Fe0.9MnxAl0.1-x)2 (x= 0~0.1) alloys were prepared from 99.9% purity Tb, Dy, Fe, Be, Mn and Al by acr-melting in a cold copper crucible under an argon atmosphere. The results indicate that the addition of beryllium improves hardness, magnetostriction l, dynamic strain coefficient d33max and lowers the corresponding field Hd33max for Tb0.3Dy0.7(Fe1-xBex)2 alloys. The optimum specimen of Be-series is that 6.67 at.% Be, and the magnetostriction is five times larger then unmodified under a magnetic field 0.5 kOe. The d33max value of the optimum specimen (256×10-9 Oe-1) is 1.5 times larger then that of original specimen (97×10-9 Oe-1), and Hd33max is improved from 1.62 kOe to 0.62 kOe. The modification by both Mn and Al improves hardness, l at low field, d33max and lowers Hd33max for Tb(Fe0.9MnxAl0.1-x)2 alloys. The x=0.04 (2.67 at.% Mn) alloy is the optimum one in Mn-Al-series, and the magnetostriction is ten times larger then that unmodified under a magnetic field 1 kOe. The d33max value of the optimum specimen increases from 210×10-9 Oe-1 to 360×10-9 Oe-1, and Hd33max is improved from 1.75 kOe to 0.56 kOe. Tb0.3Dy0.7(Fe0.9MnxAl0.1-x)2 ribbons were prepared by melt-spinning method. All of the specimens contain partial crystalline of Laves phase or rare earth rich phase, even the wheel speed achieved 40 m/s. The results indicate that strain gauge method is not suitable for measuring magnetostriction of ribbons. Tb-Fe thin films were prepared by DC magnetron sputtering from an alloy-target with different sputtering parameters, which included substrate temperature, sputtering time and power. The magnetic force microscopy was used to observe the domain structure of the samples. The domain structure versus strain effect was studied. From the domain observe, we calculated the domain wall energy per unit area and exchange const.