Magnetostriction and volume magnetostriction of sputtered Tb20Fe24Co56 film

Abstract

The magnetostriction and volume magnetostriction of sputtered amorphous Tb20Fe24Co56 (TFC) films are investigated. In recent years, knowledge of volume magnetostriction is needed in terms of actuator applications utilizing the volume magnetostriction effect. This TFC film with the composition selected in this study is known to exhibit small Joule magnetostriction in Tb-Fe-Co system, and the volume magnetostriction of Tb-Fe-Co thin film systems may be observed more significantly. A bilayer cantilever structure is used to evaluate the magnetostriction performance, which indicates that the largest magnetostriction coefficient and volume magnetostriction of the TFC films are 54 and 48 ppm at an external magnetic field of 7490 Oe, respectively. The Ar gas pressure during sputter deposition is selected to be in the range of 0.7 to 8 Pa in consideration of the deposition quality of the TFC film. The residual stress shifts to the tensile side as the Ar gas pressure increases while the stress field affects the magnetostriction performance. The value of the Joule magnetostriction of the TFC film is almost as same as the volume magnetostriction, which shows that the volume magnetostriction is the dominant mechanism of the magnetic field-induced strain. The homogeneous distribution of elements in the amorphous TFC films possibly makes the Joule magnetostriction small. Since the magnetization of the TFC film is sensitive to strain, the stress field in the in-plane direction strongly constrains the magnetic moment in the out-of-plane direction, and this constraint affects the magnetostriction and magnetization properties. This strain-sensitive magnetic film opens up new possibilities for microdevices using magnetostrictive TFC films via volume magnetostriction.