Abstract
Magnetostriction is the emergence of a mechanical deformation induced by an external magnetic field. The conversion of magnetic energy into mechanical energy via magnetostriction at the nanoscale is the basis of many electromechanical systems such as sensors, transducers, actuators, and energy harvesters. However, cryogenic temperatures and large magnetic fields are often required to drive the magnetostriction in such systems, rendering this approach energetically inefficient and impractical for room-temperature device applications. Here, we report the experimental observation of giant magnetostriction in single-crystal nickel nanowires at room temperature. We determined the average values of the magnetostrictive constants of a Ni nanowire from the shifts of the measured diffraction patterns using the 002 and 111 Bragg reflections. At an applied magnetic field of 600 Oe, the magnetostrictive constants have values of λ100 = −0.161% and λ111 = −0.067%, two orders of magnitude larger than those in bulk nickel. Using Bragg coherent diffraction imaging (BCDI), we obtained the three-dimensional strain distribution inside the Ni nanowire, revealing nucleation of local strain fields at two different values of the external magnetic field. Our analysis indicates that the enhancement of the magnetostriction coefficients is mainly due to the increases in the shape, surface-induced, and stress-induced anisotropies, which facilitate magnetization along the nanowire axis and increase the total magnetoelastic energy of the system.
Highlights
Significant interest in magnetostrictive nanostructures dates back to the mid-1970s1, with many reports on thin films, multilayers, and superlattices exhibiting large magnetostriction[2,3,4]
The average values of the magnetostrictive strain were obtained by tracking the relative shifts of the 002 and 111 Bragg peaks as a function of the applied magnetic field
The λ100 and λ111 magnetostrictive coefficients were measured for a single-crystal nickel nanowire using coherent X-ray diffraction at the 34-ID-C end station of the Advanced Photon Source
Summary
Significant interest in magnetostrictive nanostructures dates back to the mid-1970s1, with many reports on thin films, multilayers, and superlattices exhibiting large magnetostriction[2,3,4]. In these planar systems, a large magnetostrictive strain on the order of 0.1% was observed for textured Co0.75Fe0.25 thin films[5], while Tb0.3Dy0.7Fe2 bulk crystals showed magnetostriction λ111 values of ~0.16%6,7. The dependence of the magnetostriction value on the stoichiometry of Fe-Ga alloys has been extensively studied, and in Fe83Ga17, the λ100 magnetostriction coefficient can reach 0.02% at room temperature[9].
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