We have demonstrated a general framework for realizing and modulating perpendicular magnetic anisotropy in a rare-earth-element and heavy-metal-free material system. Using GaAs(001)/Fe(001) template, we have developed a synthesis scheme to produce epitaxial body center tetragonal Fe-N with (001) texture. By varying the N doping concentration, the crystal tetragonality (c/a) can be tuned in a relatively wide range. It is found that the Fe-N layer developed a strong perpendicular magnetic crystalline anisotropy (MCA) as it approaches the iron nitride interstitial solubility limit. Further annealing significantly improves the MCA due to the formation of chemically ordered Fe₁₆N₂. In addition to realizing an MCA up to 10⁷ erg/cm³, the spin polarization ratio (P {~} 0.52), as probed directly by a point-contact Andreev reflection (PCAR) method, even shows a moderate increase in comparison with normal metal Fe (P {~} 0.45). These combined properties make this material system a promising candidate for applications in spintronic devices and also potential rare-earth-element free magnets.
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Ji et al. (2011) studied this question.