Research ArticlePHYSICS

Giant perpendicular magnetic anisotropy in Fe/III-V nitride thin films

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Science Advances  30 Mar 2018:
Vol. 4, no. 3, eaar7814
DOI: 10.1126/sciadv.aar7814

Figures

  • Fig. 1 PMA of Fe(1ML)/III-V nitrides.

    (A) Surface structures of one-monolayer (1ML) Fe deposited on Embedded Image N-terminated surface of III-V nitride XN (X = B, Al, Ga, and In) substrate in top, side, and perspective views, respectively. In top view, three dash-dotted lines indicate three mirror planes of the C3v point group on Fe. (B) Crystal field diagram for Fe(3d)’s spin majority (spin up) and minority (spin down) channels. The spin minority channel is further split by SOC. EF refers to the Fermi level. (C) The relative total energy per unit cell (u.c.) of Fe(1ML)/III-V nitride thin film as a function of Embedded Image, where θ denotes the angle between magnetization orientation and the z direction. Relative energy at Embedded Image gives the value of PMA. The dotted curves are their fit to Embedded Image.

  • Fig. 2 Charge distribution and electronic structure of Fe(3d) orbitals in Fe(1ML)/GaN.

    (A) The positive and (B) negative part of the charge difference between the total charge density of Fe(1ML)/GaN and the sum of charge densities of a suspended 1ML Fe and pure GaN supercell. Charge deficiency in xz/yz-like orbitals shown in (A) is transferred to x2y2/xy-like orbitals shown in (B). (C to F) Orbital-resolved projected density of state (PDOS) of 3z2r2, xz/yz, and x2y2/xy orbitals, respectively, in the absence of SOC. The bandwidth Δ of x2y2/xy is labeled in (F). (E) PDOS for Fe(3d) orbitals with SOC included. Positive and negative values of PDOS refer to spin majority and spin minority channels, respectively, and the Fermi level is set to zero. (G) Occupation number of each Fe(3d) orbital and (H) PMA as a function of the Hubbard U when SOC is included.

  • Fig. 3 Electronic structures of 1ML Fe on BN, AlN, and InN, respectively.

    (A to C) PDOS of x2y2/xy orbitals without SOC. The bandwidth in the spin minority channel is indicated by double arrows. (D to F) PDOS of Fe(3d) with SOC. In (D), the shadow region gives the projection onto x2y2/xy orbitals where the magnitude of splitting is indicated by the double arrow.

  • Fig. 4 Comparison of electronic structures between GGA-PBE, GGA + U, and HSE06.

    DOS (gray dashed line) and PDOS (solid blue line) of Fe(1ML)/GaN without SOC derived by (A) GGA-PBE, (B) GGA + U at U = 4.0 eV and (C) HSE06, respectively. Consistency between (B) and (C) shows that GGA + U at U = 4.0 eV can well describe Fe(3d) orbitals in this system.

Tables

  • Table 1 PMA and relevant magnetic properties for each Fe(1ML)/III-V nitride.

    The values of Ku1, Ku2, total PMA in units of millielectron volt per unit cell and millijoule per square meter, spin moments (ms), orbital moments (ml), and occupation number Embedded Image of the Embedded Image-dominated state in spin minority are listed.

    Fe/BNFe/AlNFe/GaNFe/InN
    Ku1 (meV/u.c.)22.518.116.217.5
    Ku2 (meV/u.c.)1.616.216.436.2
    PMA (meV/u.c.)24.134.332.553.7
    PMA (mJ/m2)59.156.651.371.9
    msB)3.563.833.843.84
    mlB)0.911.441.541.51
    Embedded Image0.7240.8540.9040.930
  • Table 2 Bader charges on Fe and the top N atom.

    Bulk refers to the bulk Fe and GaN; surface refers to the clean GaN Embedded Image N-terminated surface; interface refers to 1ML Fe on the GaN substrate. The last column gives the results with SOC included.

    Bader chargeBulkSurfaceInterfaceInterface SOC
    Fe8.007.617.60
    N in GaN6.526.156.546.54

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