Giant tunability of magnetoelasticity in Fe4N system as a platform to unveil correlation between magnetostriction and magnetic damping

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Flexible spintronics has opened avenues to promising devices and applications in the field of wearable electronics. For miniaturized strain sensors exploiting the spintronic function, the magnetoelasticity linking magnetism and lattice distortion is a vital property. Here we report the demonstration that the magnetoelastic properties of Fe4N can be significantly varied by partially replacing Fe with Co or Mn. The high quality Fe4N film exhibits large negative magnetostriction along the [100] direction (λ 100) of −121 ppm while Fe2.3Co1.7N shows λ 100 of + 46 ppm. The strong correlation between λ 100 and magnetic damping (α) is found. The enhanced extrinsic term of α is attributable to the large two magnon scattering coming from the large magnetostriction. In addition, the density of states at the Fermi level plays a primal role to determine both λ 100 and the intrinsic term of α. Thanks to the giant tunability and the bipolarity of magnetoelasticity, magnetic nitrides are candidate materials for high-sensitive spintronic strain sensors.