Correlation of electronic structure and magnetic moment in Fe16N2: First-principles calculations

A review of high magnetic moment thin films for microscale and nanotechnology applications

“…292,293 The mixed nature of the FeN compounds, which makes it very hard to actually (quantitatively) determine the a 00 thicker layers or foils, 294 and also the limited thickness of MBE-grown samples impacting on the accuracy of saturation magnetisation measurements, still keep the error bars on measured magnetisation values unpleasantly large. First theoretical explanation attempts for a saturation moment beyond the Slater-Pauling limit were given by Ji et al 285,295 based on partially localised electron states due to the octahedral structure of FeN clusters in a 00 Fe 16 N 2 (see also Sims et al 296 and Shi et al 297 ); however, XMCD measurements which were supposed to corroborate the claim did only confirm that there are increased-moment Fe sites in ordered Fe 16 N 2 and disordered Fe 8 N crystals alike. 298 In a 2013 study, Ji et al 299 however, no significant magnetisation since the overall a 00 phase content was only 22% after annealing.…”

Re-examining the giant magnetization density in α′′-Fe16N2 with the SCAN+U method

“…Recent Density Functional Theory (DFT) studies of α′′-Fe 16 N 2 based on the Generalized Gradient Approximation (GGA) corrected by the Hubbard parameter U have been reported by Bhattacharjee et al , 20 Islam et al , 21 and Stoeckl et al 22 These investigations and other DFT+ U calculations 19,23–27 show, as expected, that the Fe magnetic moment increases with the strength of correlation effects described by U . However, increasing U expands the equilibrium volume when the geometry is optimized, 22 so that the magnetization density M s does not increase beyond the Slater–Pauling limit of 2.45 T.…”

“…[56][57][58][59] Recently, this problem has been cured by introducing a de-orbitalized SCAN potential. 60 The de-orbitalization condition is especially important at the Fermi Surface of itinerant ferromagnetic materials as shown by eqn (24) in the paper by Gunnarsson and Lundqvist. 61 This constraint has been discussed also by Barbiellini and Bansil.…”

“…Successful attempts to prepare a 00 -Fe 16 N 2 samples have been reviewed by Wang 16 and include the synthesis of thick a 00 -Fe 16 N 2 foils. 17 The most recent X-ray and neutron diffraction results by Hang et al report saturation magnetizations of 2.6-2.9 T, 18 and have been reproduced by a cluster-atom model introduced by Ji et al 19 Recent Density Functional Theory (DFT) studies of a 00 -Fe 16 N 2 based on the Generalized Gradient Approximation (GGA) corrected by the Hubbard parameter U have been reported by Bhattacharjee et al, 20 Islam et al, 21 and Stoeckl et al 22 These investigations and other DFT+U calculations 19,[23][24][25][26][27] show, as expected, that the Fe magnetic moment increases with the strength of correlation effects described by U. However, increasing U expands the equilibrium volume when the geometry is optimized, 22 so that the magnetization density M s does not increase beyond the Slater-Pauling limit of 2.45 T.…”

First principles study of interactions of oxygen–carbon–vacancy in bcc Fe*

“…When the concentration exceeds their solubility limit, the solutes tend to precipitate as carbides, nitrides, or oxides. [27] These precipitates, such as Fe 3 C, [28][29][30][31][32] Fe 5 C 2 , [28,31] Fe 4 N, [33][34][35] Fe 2−3 N, [33,34,36,37] Fe 16 X 2 (X = C or N), [38][39][40] Fe 3 O 4 , [41] Fe 2 O 3 , [42] Cr 23 C 6 , [43,44] Cr 7 C 3 , [32,[43][44][45] Cr 2 N, [46] and CrN [47] have been extensively investigated. These compounds play a key role in determining the mechanical properties [27] (hardness, wear resistance, etc.)…”