High magnetic moments and anisotropies forFexCo1−xmonolayers on Pt(111)

Abstract

The magnetism of 1-ML-thick films of Fe x Co 1−x on Pt͑111͒ was investigated both experimentally, by x-ray magnetic circular dichroism and magneto-optical Kerr effect measurements, and theoretically, by firstprinciples electronic structure calculations, as a function of the film chemical composition. The calculated Fe and Co spin moments are only weakly dependent on the composition and close to 3 B / atom and 2 B / atom, respectively. This trend is also seen in the experimental data, except for pure Fe, where an effective spin moment of only S eff = ͑1.2Ϯ 0.2͒ B / atom was measured. On the other hand, both the orbital moment and the magnetic anisotropy energy show a strong composition dependence with maxima close to the Fe 0.5 Co 0.5 stoichiometry. The experiment, in agreement with theory, gives a maximum magnetic anisotropy energy of 0.5 meV/atom, which is more than 2 orders of magnitude larger than the value observed in bulk bcc FeCo and close to that observed for the L1 0 phase of FePt. The calculations clearly demonstrate that this composition dependence is the result of a fine tuning in the occupation number of the d x 2 −y 2 and d xy orbitals due to the Fe-Co electronic hybridization.

Magnetic anisotropy of Fe and Co adatoms and Fe clusters magnetically decoupled fromNi3Al(111)by an alumina bilayer

“…Application of the XMCD sum rules allows to extract independently the orbital magnetic moment L and the effective spin moment S ef f = S +7D, where S is the spin moment and D the spin dipole moment. [18][19][20] Using the number of d holes of bulk Ni h d = 1.66 ͑Ref. 21͒ we obtain L = 0.047 B / Ni atom and S = 0.357 B / Ni atom when neglecting the dipolar term.…”

Magnetism and morphology of Co nanocluster superlattices onGdAu2/Au(111)–(13×13)

“…At T = 85 K the total atomic moments steeply rise between 2.0 and 3.0 ML until they saturate for 3.7 ML at (1.8 ± 0.2)μ B per atom, quite close to the Co bulk value (1.72μ B ) and slightly smaller than the Co monolayer value (2.1-2.3μ B [34,35]). Data points interpolation identifies 2.2 ML as the onset of remanence at 85 K. At this coverage the clusters extend at least over three moiré cells and they cover an area of more than 1700Å…”

“…4(e). They are situated at 0.13-0.16, thus comparing well to Co monolayers on Rh(111) with μ L /μ S+7D = 0.16 ± 0.04, and on Pt(111) with 0.17 ± 0.04 [34,35].…”

Path to collapse for an isolated Néel skyrmion

“…For a thin film, d ij = d(û ij ×ẑ) 2,29 , withû ij the unit vector between sites i and j and z the normal to the plane. The third term is the uniaxial anisotropy, with constant k, the fourth term is the dipolar coupling and the last term is the Zeeman energy in field H. The parameters are: µ at = S i = 2.1 µ B /atom [30][31][32][33] , J = 29 meV/bond 30 , d = 1.5 meV/bond [25][26][27] , k = 0.4 meV/atom 31,33 (including the shape anisotropy 34 , the effective anisotropy is 0.276 meV/atom in good agreement with literature 31,33 ). The sample is limited by free boundary conditions and the size has been chosen so that an isolated skyrmion is not affected by the edges (no morphology nor energy changes seen for larger calculation box sizes).…”