Giant magnetostriction in annealed Co1−xFex thin-films

• DOI: 10.1038/ncomms1529
• Publication Date: 2011-11-01T16:41:43Z
• Authors: Dwight Hunter; Will Osborn; Ke Wang; Nataliya Kazantseva; Jason Hattrick-Si...; Richard Suchoski; Ryota Takahashi; Marcus L. Young; Apurva Mehta; Leonid A. Bendersky; Sam E. Lofland; Manfred Wuttig; Ichiro Takeuchi
• Keywords: Other Chemical Engineering; ferroelectrics; Other Materials Science and Engineering; Chemical Engineering; Electrical and Computer Engineering; magnetostriction; 530; 01 natural sciences; morphotropic phase boundaries; Engineering; thin films; Materials Science and Engineering; oxides; piezoelectric materials; 0103 physical sciences; metallic alloys; heterogeneity; Electromagnetics and Photonics

Chemical and structural heterogeneity and the resulting interaction of coexisting phases can lead to extraordinary behaviours in oxides, as observed in piezoelectric materials at morphotropic phase boundaries and relaxor ferroelectrics. However, such phenomena are rare in metallic alloys. Here we show that, by tuning the presence of structural heterogeneity in textured Co(1-x)Fe(x) thin films, effective magnetostriction λ(eff) as large as 260 p.p.m. can be achieved at low-saturation field of ~10 mT. Assuming λ(100) is the dominant component, this number translates to an upper limit of magnetostriction of λ(100)≈5λ(eff) >1,000 p.p.m. Microstructural analyses of Co(1-x)Fe(x) films indicate that maximal magnetostriction occurs at compositions near the (fcc+bcc)/bcc phase boundary and originates from precipitation of an equilibrium Co-rich fcc phase embedded in a Fe-rich bcc matrix. The results indicate that the recently proposed heterogeneous magnetostriction mechanism can be used to guide exploration of compounds with unusual magnetoelastic properties.