Influence of the TbFe2 crystallization on the magnetic and magnetostrictive properties of (Fe3Ga/TbFe2)n heterostructures

In this work we have investigated (Fe3Ga/TbFe2)n multilayers grown by sputtering at room temperature. These multilayers exhibit a large coercivity associated to the crystalline TbFe2 Laves phase. To reduce the coercivity it is necessary to control the crystallization of that material. In this work, we focus on the analysis of the properties of the TbFe2 layers. In the as-grown heterostructures we have found evidence of nanoaggregates in the TbFe2 layers. The Fe3Ga thickness and the thermal treatments have an influence on the volume of these nanoprecipitates. In the annealed samples, when increasing the Fe3Ga thickness we observe a decrease in the nanoaggregate volume and thus in the coercivity. The experimental results indicate that the crystallization of the TbFe2 depends on the Tb diffusion promoted by the thermal treatment and on the stiffness factor (Y/α) of the Fe3Ga layer. The magnetostrictive properties are also strongly influenced by the crystallization of the TbFe2. We have achieved a maximum magnetostriction constant of nearly 550 ppm with a coercive field close to 400 Oe.