Magnetic and magnetoelastic behavior of epitaxial TbFe2/YFe2 bilayers - art. no. 054417

We report on magnetic hysteresis and magnetoelastic stress measurements on a series of (110) TbFe2(t)/YFe2 (1000 Angstrom) bilayers (t = 300, 600, 100 0, and 1300 Angstrom) grown by molecular-beam epitaxy. The magnetization cu rves show large jumps that we have explained as due to the different magnet ization contribution of both kinds of magnetically soft (YFe2) and hard (Tb Fe2) blocks, which, on the other hand, hardly show magnetic interaction for t>300 Angstrom. In these cases, the hysteresis loop of the individual TbFe 2 block is determined. The magnetoelastic stress measurements were performe d along the main symmetry directions by using a cantilever capacitive metho d. They allowed us to determine the whole second-order magnetoelastic stres s parameters: b(o) [associated to combined volume and tetragonal magnetostr iction (MS)], b(1) (to tetragonal MS alone), and b(2) (to rhombohedral MS), at temperatures between 10 and 300 K. The b(o) values are about one order of magnitude lower than the b(1) and b(2) ones. \b(2)\ smoothly rises on in creasing the TbFe2 block thickness, whereas b(1)(t) peaks at similar to 100 0 Angstrom. A competition between volume and interface magnetoelastic stres ses could explain this fact. The thermal dependence of b(1) and b(2) indica tes a single-ion crystal-electric-field origin for the magnetoelastic coupl ing and suggests a somehow rough interface between TbFe2 and YFe2 blocks.