Structure and magnetism of single-phase epitaxialγ′−Fe4N

Abstract

Single phase epitaxial pure ␥Ј-Fe 4 N films are grown on MgO ͑001͒ by molecular beam epitaxy of iron in the presence of nitrogen obtained from a radio frequency atomic source. The epitaxial, single phase nature of the films is revealed by x-ray diffraction and by the local magnetic environment investigated by Mössbauer spectroscopy. The macroscopic magnetic properties of the ␥Ј-Fe 4 N films are studied in detail by means of transverse Kerr effect measurements. The hysteresis loops are consistent with the cubic atomic structure, displaying easy ͓100͔ magnetization directions. The films are single domain at remanence, and the reversal is dominated by 180°or 90°domain wall nucleation and propagation, depending on the applied field direction. When 90°domain walls are responsible for the magnetization reversal, this proceeds in two stages, and the measured coercive fields vary accordingly. Magnetic domain observations reveal the two distinct reversal -driven by 180°or 90°domain walls-modes displaying large domains, of the order of mm. From magnetometer techniques, the saturation magnetization, 0 M s , is measured to be 1.8 T. A magneto-optical torque technique is used to obtain a value of the anisotropy constant of 2.9ϫ10 4 J/m 3 .

Electronic structure of ultrathinγ′−Fe4N(100) films epitaxially grown on Cu(100)

“…There is general agreement in the magnetic properties of ␥Ј-Fe 4 N. 3,8 Surprisingly, its electronic structure is controversial. Previous calculations 9,10 disagree with respect to whether the bonding is covalent or ionic, the degree of charge transfer, or the magnetic moment.…”

Predicted stability, structures, and magnetism of 3d transition metal nitrides: the M4N phases

“…First, M 4 N nitrides with M ¼ Fe, Co and Ni, have unique electronic and magnetic properties and consequently have potential applications as magnetic recording materials, [1][2][3][4][5] as spin carriers in spintronics [3][4][5][6] and even as catalysts used for photocatalytic water splitting. 7 Second, there are two possible phases for M 4 N (the I-phase and the II-phase) that are structurally difficult to distinguish but that can have very different physical properties.…”

Electrical detection of magnetic domain wall in Fe4N nanostrip by negative anisotropic magnetoresistance effect

“…37 The material parameters used for the simulations were the magnetization M S ¼ 1.43 MA/m, the crystalline magnetic anisotropy constant K C ¼ 3.0 Â 10 4 J/m 3 , and the exchange stiffness A ¼ 15 pJ/m. Among these, the M S and K C were measured values, 35 while the value of A for Fe 4 N was approximated from that for Fe using the relationship that A is nearly proportional to T C . 38 The damping constant was set to a ¼ 1 to accelerate the calculation with the expectation that the value of a has no effect on equilibrium states.…”

“…33,34 This method is available not only for IMA materials but also for PMA materials, enabling determination of the DW position from the slope of the resistivity versus magnetic flux density minor loop. The Fe 4 N material exhibits IMA, 35 but there has been no report on the electrical detection of DWs in Fe 4 N nanostrips, which is of essential importance to detect CIDM in Fe 4 N. This work detects the DR of ferromagnetic Fe 4 N nanostrips depending upon the presence or absence of a DW between two electrodes mounted on the nanostrips. Electrons scatter in the DW differently from those in the domains adjacent to the DW because the direction of magnetization is different between them.…”