Simultaneous tuning of the magnetic anisotropy and thermal stability of [Formula: see text]-phase Fe[Formula: see text]N[Formula: see text].

ABSTRACT

Simultaneously enhancing the uniaxial magnetic anisotropy ([Formula see text]) and thermal stability of [Formula see text]-phase Fe[Formula see text]N[Formula see text] without inclusion of heavy-metal or rare-earth (RE) elements has been a challenge over the years. Herein, through first-principles calculations and rigid-band analysis, significant enhancement of [Formula see text] is proposed to be achievable through excess valence electrons in the Fe[Formula see text]N[Formula see text] unit cell. We demonstrate a persistent increase in [Formula see text] up to 1.8 MJ m[Formula see text], a value three times that of 0.6 MJ m[Formula see text] in [Formula see text]-Fe[Formula see text]N[Formula see text], by simply replacing Fe with metal elements with more valence electrons (Co to Ga in the periodic table). A similar rigid-band argument is further adopted to reveal an extremely large [Formula see text] up to 2.4 MJ m[Formula see text] in (Fe[Formula see text]Co[Formula see text])[Formula see text]N[Formula see text] obtained by replacing Co with Ni to Ga. Such a strong [Formula see text] can also be achieved with the replacement by Al, which is isoelectronic to Ga, with simultaneous improvement of the phase stability. These results provide an instructive guideline for simultaneous manipulation of [Formula see text] and the thermal stability in 3d-only metals for RE-free permanent magnet applications.