Sensing anisotropic stresses with ferromagnetic nanowires

Abstract

We have measured the temperature variation of the magnetic anisotropy of Ni nanowires (Ni NWs) embedded in freestanding porous anodized aluminum oxide membranes, using DC magnetometry and ferromagnetic resonance. Both techniques show a significant reduction of the uniaxial anisotropy with decreasing temperature. This decrease can be explained by magnetoelastic effects, as Ni NWs are subjected to stress due to the difference in thermal expansion coefficients between the nanocomposite materials. Matching our experimental findings with previously measured thermal strains along the Ni NW axis led us to estimate the perpendicular stress. Thus, we postulate the Ni NWs as nanometric differential stress sensors.