The magnetic and magnetoelastic properties of melt-spun TbFe_2 based alloys and their temperature dependencies

Crystalline TbFe_2 exhibits huge values of magnetostriction even at room temperature. The large single-ion anisotropy of terbium responsible for the observed value of magnetostriction also produces a large magnetic anisotropy yielding hard magnetic properties. The objective of the present study is the production of soft magnetic giant magnetostrictive terbium - iron alloy ribbons and the investigation of their magnetic and magnetoelastic properties. Melt-spun ribbons have a high potential for applications due to their softer magnetic properties and dimensions allowing lower applied fields and higher operating frequencies. Soft magnetic properties of Tb-Fe alloys can only be obtained by destroying the crystalline order, i.e. by producing an amorphous structure. In order to prepare bulk amorphous material the melt-spinning technique was employed. However, to produce amorphous terbium - iron alloy ribbons by melt-spinning a certain amount of a glass former, e.g. boron or silicon, must be added to prevent crystallisation. The main focus of this work is on the influence of an increasing boron concentration on the magnetic and magnetoelastic properties of (TbFe_2)_1_0_0_-_xB_x, boron being the best known and most effective glass former. For the investigation of the magnetostriction of TbFe_2 based alloys prepared as ribbons a capacitance cell was built enabling measurements on single ribbon pieces. It is shown that reducing the structural correlation length (reducing crystalline order) can significantly reduce the macroscopic magnetic anisotropy, as evident in the reduced coercivity, but large magnetostrictive strains are retained. It is interesting that with 3 at. % boron present the magnetostrictive strains have already reached the levels found in polycrystalline TbFe_2. The macroscopic anisotropy is most effectively reduced in amorphous alloys. On the other hand when the ribbons show signs of crystallinity at 3 at. % boron the RT coercivity is still reduced by a factor of 5 in comparison to polycrystalline TbFe_2 but accompanied by a much smaller reduction of the magnetostrictive strain. (author)Available from British Library Document Supply Centre-DSC:DXN037017 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo