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The effect of electron confinement on the magnetocrystalline anisotropy of ultrathin bcc Fe films is explored by combining photoemission spectroscopy, x-ray magnetic circular dichroism, and magneto-optical Kerr effect measurements. Pronounced thickness-dependent variations in the magnetocrystalline anisotropy are ascribed to periodic changes in the density of states at the Fermi level, induced by quantization of ${d}_{xz}$, ${d}_{yz}$ out-of-plane orbitals. Our results reveal a direct correlation between quantum well states, the orbital magnetic moment, and the magnetocrystalline anisotropy.

Tetragonal distortion in Fe 1-x Cox alloy films grown epitaxially on Rh(001) substrates results in a strong perpendicular magnetic anisotropy. Since the perpendicular magnetic anisotropy varies with the Fe 1-x Co x film composition, one can grow multilayer structures with ferromagnetic films sequentially showing either an in-plane (e.g., Fe) or out-of-plane (e.g., Fe 0.5 Co 0.5 ) easy-magnetization axis. The Rh spacers mediate an interlayer coupling which couples the magnetizations either ferromagnetically or antiferromagnetically, depending on the spacer thickness. When the anisotropy energy is compatible to the coupling, it produces nonorthogonal magnetization configurations which vary under a small change of the external magnetic field.

A self-corrugated Cu(3)N-Cu(110) molecular network shows the potential to overcome the element dependence barrier as demonstrated by epitaxial growth of atomic nanowires (approximately 1 nm in width) among various 3d, 4d, and 5d elements. Scanning tunneling microscopy shows that all of the investigated atomic nanowires share an identical structure, featuring uniform width, height, orientation and the same minimum separation distance. Ab initio study reveals that the formation mechanism of atomic nanowires can be directly attributed to a strain relief guided asymmetric occupation of atoms on the originally symmetric crest zone of the corrugated network.

The magnetic anisotropy of Fe film grown on vicinal Ag(1,1,10) surfaces was studied with the in situ magneto-optic Kerr effect. Below 200 K, strong oscillations of the uniaxial magnetic anisotropy as a function of Fe thickness with a period of 5.7 monolayers are found, which can even cause the easy magnetization axis to oscillate between perpendicular and parallel to the steps. Such novel oscillation of the anisotropy is attributed to the quantum well states of d-band electrons at the Fermi level in the Fe film. This is unlike the previously observed oscillatory behaviors of ferromagnetic films caused by the quantum well states in nonmagnetic interfacing layers.

We studied tetragonally distorted ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}$ alloy films on Rh(001), which show a strong perpendicular anisotropy in a wide thickness and composition range. Analyzing x-ray magnetic circular dichroism spectra at the ${L}_{3,2}$ edges we found a dependence of the Co magnetic orbital moment on the chemical composition of the ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}$ alloy films, with a maximum at $x=0.6$. For this composition, we observed an out-of-plane easy axis of magnetization at room temperature for film thickness up to 15 monolayers. Since both the magnetic orbital moment and the anisotropy energy show similar composition dependence, it confirms that both quantities are directly related. Our experiments show that the adjustment of the Fermi level by a proper choice of the alloy composition is decisive for the large magnetic orbital moment and for a large magnetic anisotropy in a tetragonally distorted lattice.

We grew tetragonally distorted FexCo1-x alloy films on Pd(001). Theoretical first-principles calculations for such films predicted a high saturation magnetization and a high uniaxial magnetic anisotropy energy for specific values of the lattice distortion c/a and the alloy composition x. The magnetic anisotropy was investigated using the magneto-optical Kerr effect. An out-of-plane easy axis of magnetization was observed for Fe0.5Co0.5 films in the thickness range of 4 to 14 monolayers. The magnetic anisotropy energy induced by the tetragonal distortion is estimated to be almost 2 orders of magnitude larger than the value for bulk FeCo alloys. Using LEED Kikuchi patterns, a change of the easy axis of magnetization can be related to a decrease of the tetragonal distortion with thickness.