Development of giant low-field magnetostriction in a-TerfecoHan-based single layer, multilayer and sandwich films

• Published in: Journal of magnetism and magnetic materials Vol. 242-245; pp. 1411 - 1417
• Main Author: Duc, N.H.
• Format: Journal Article
• Language: English
• Published: 01.04.2002
• ISSN: 0304-8853
• DOI: 10.1016/S0304-8853(01)00961-1

Giant magnetostriction in low magnetic field has been achieved with different approaches, among which single, multilayer and sandwich films with rare-earth base are considered as most promising ones. Enhancement of the 3d(Fe,Co)-magnetic moment with respect to those of 3d(Fe) and 3d(Co) strengthens the Tb-FeCo exchange energies in amorphous Tb(Fe sub(0.55)Co sub(0.45 )) sub(1.5) (named as a-TerfecoHan) films. This is thought to cause diminishing of the Tb-sperimagnetic cone-angle and, thus, leading to enhancement of the magnetostriction. Indeed, a saturation magnetostriction of lambda ( gamma ,2)[similar to]10 super(-3) has been obtained. After annealing, a parallel magnetostrictive susceptibility of Chi ( lambda parallel ) = 1.8 x 10 super(-2)T super(-1) has been achieved at mu sub(o)H = 10mT. TbFeCo/YFe multilayers combining exchange-coupled giant magnetostrictive TerfecoHan layers and large-magnetisation Y sub(0.2)Fe sub(0.8) ones exhibit an excellent magnetic and magnetostrictive softness. Subsequent annealing at 350 degree C leads to the relaxation of the a-TbFeCo layers and to a nanocrystallisation of the YFe layers. In this state, a magnetic coercive field mu sub(o)H(C) = 0.3mT and a huge magnetostrictive susceptibility, Chi ( lambda parallel ) = 13x10 super(-2)T super(-1) have been obtained. Mossbauer studies indicate that the magnetic softness as observed is associated to the evolution of the nanocrystalline Fe-particles. Magnetostriction is also presented for Fe/TerfecoHan/Fe sandwiches. In this case, giant magnetostriction is already developed at low fields in as-deposited films. Technologically, this seems to be one of the simplest ways to prepare magnetostrictive films for microsystem applications. copyright 2002 Elsevier Science B.V. All rights reserved.