Giant tunability of magnetoelasticity in Fe$_4$N system: Platform for unveiling correlation between magnetostriction and magnetic damping

TL;DR

This study demonstrates that the magnetoelastic properties of Fe4N can be extensively tuned by substituting Fe with Co or Mn, revealing a strong correlation between magnetostriction and magnetic damping, with implications for spintronic strain sensors.

Contribution

It introduces a method to significantly tune magnetoelasticity in Fe4N through element substitution, enabling detailed study of its correlation with magnetic damping.

Findings

Magnetostriction in Fe4N varies from -121 ppm to +46 ppm with substitution.

A strong correlation between magnetostriction and magnetic damping is observed.

Large two magnon scattering is linked to high magnetostriction.

Abstract

Flexible spintronics has opened new avenue to promising devices and applications in the field of wearable electronics. Particularly, miniaturized strain sensors exploiting the spintronic function have attracted considerable attention, in which the magnetoelasticity linking magnetism and lattice distortion is a vital property for high-sensitive detection of strain. This paper reports the demonstration that the magnetoelastic properties of Fe$_4$N can be significantly varied by partially replacing Fe with Co or Mn. The high quality Fe$_4$N film exhibits large negative magnetostriction along the [100] direction ($\lambda_{100}$) of -121 ppm while Fe$_{3.2}$Co$_{0.8}$N shows $\lambda_{100}$ of +46 ppm. This wide-range tunability of $\lambda_{100}$ from -121 to +46 across 0 allows us to thoroughly examine the correlation between the magnetoelasticity and other magnetic properties. The strong correlation between $\lambda_{100}$ and magnetic damping ($\alpha$) is found. The enhanced extrinsic term of $\alpha$ 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 $\lambda_{100}$ and the intrinsic term of $\alpha$. Thanks to the giant tunability and the bipolarity of magnetoelasticity, magnetic nitrides are candidate materials for high-sensitive spintronic strain sensors.