Spin and orbital magnetic moments of size-selected iron, cobalt, and nickel clusters

Abstract

Spin and orbital magnetic moments of cationic iron, cobalt, and nickel clusters have been determined from x-ray magnetic circular dichroism spectroscopy. In the size regime of n = 10 − 15 atoms, these clusters show strong ferromagnetism with maximized spin magnetic moments of 1 µB per empty 3d state because of completely filled 3d majority spin bands. The only exception is Fewhere an unusually low average spin magnetic moment of 0.73 ± 0.12 µB per unoccupied 3d state is detected; an effect, which is neither observed for Co + 13 nor Ni + 13 . This distinct behavior can be linked to the existence and accessibility of antiferromagnetic, paramagnetic, or nonmagnetic phases in the respective bulk phase diagrams of iron, cobalt, and nickel. Compared to the experimental data, available density functional theory calculations generally seem to underestimate the spin magnetic moments significantly. In all clusters investigated, the orbital magnetic moment is quenched to 5 − 25 % of the atomic value by the reduced symmetry of the crystal field. The magnetic anisotropy energy is well below 65 µeV per atom.

Copper-doping effects in electronic structure and spectral properties of SmNi5

“…In the calculations we obtained significant magnetic moments of samarium and almost negligible moments of nickel with the maximum orbital moment of 0.05 µ B on the Ni ions similar to previous experimental and theoretical data, e.g., [10]. Since spin-orbit coupling in the 4f shell of samarium was explicitly taken into account in the LDA+U+SO method, total magnetic moment can be calculated including the orbital component [11].…”

Electronic ground states of Fe2+ and Co2+ as determined by x-ray absorption and x-ray magnetic circular dichroism spectroscopy

“…The most intense product ion that results from 2p core excitation and relaxation is the atomic dication for both Fe For XMCD spectroscopy, the ion trap is placed inside the homogeneous magnetic field (µ 0 H = 5 T) of a superconducting solenoid. [35][36][37][38][39][40]44 Following the standard procedures, the XMCD spectrum is obtained as the difference of x-ray absorption spectra that are recorded with parallel and antiparallel orientation of the photon helicity relative to the direction of the applied magnetic field. The isotropic x-ray absorption spectrum is obtained by taking the average of the spectra of both photon helicities.…”

“…In particular for free as determined by gasphase x-ray magnetic circular dichroism (XMCD) spectroscopy [34][35][36][37][38][39][40] that was only recently introduced for free molecular ions. 39,40 All states that are found in our study carry significant orbital angular momentum that disagrees with theoretical preferences for Σ states.…”

Correlation effects and orbital magnetism of Co clusters

“…As a result, a detailed knowledge of orbital magnetism is crucial in designing new materials with desired hardness and saturation moments. Most interestingly, recent XMCD experiments [9,10] on transition-metal clusters showed huge orbital moments in comparison with their bulk counterparts. Hence these systems may possess a large magnetic anisotropy energy, which makes them potentially interesting for several technological applications.…”