Structurally driven magnetic state transition of biatomic Fe chains on Ir(001)

Abstract

Using first-principles calculations, we demonstrate that the magnetic exchange interaction and the magnetocrystalline anisotropy of biatomic Fe chains grown in the trenches of the ͑5 ϫ 1͒ reconstructed Ir͑001͒ surface depend sensitively on the atomic arrangement of the Fe atoms. Two structural configurations have been considered which are suggested from recent experiments. They differ by the local symmetry and the spacing between the two strands of the biatomic Fe chain. Since both configurations are very close in total energy they may coexist in experiment. We have investigated collinear ferro-and antiferromagnetic solutions as well as a collinear state with two moments in one direction and one in the opposite direction ͑↑↓↑-state͒. For the structure with a small interchain spacing, there is a strong exchange interaction between the strands and the ferromagnetic state is energetically favorable. In the structure with larger spacing, the two strands are magnetically nearly decoupled and exhibit antiferromagnetic order along the chain. In both cases, due to hybridization with the Ir substrate the exchange interaction along the chain axis is relatively small compared to free-standing biatomic iron chains. The easy magnetization axis of the Fe chains also switches with the structural configuration and is out-of-plane for the ferromagnetic chains with small spacing and along the chain axis for the antiferromagnetic chains with large spacing between the two strands. Calculated scanning tunneling microscopy images and spectra suggest the possibility to experimentally distinguish between the two structural and magnetic configurations.

An ab initio study of the magnetic and electronic properties of Fe, Co, and Ni nanowires on Cu(001) surface

“…Interestingly, both E 1 and E 2 are positive in the Fe nanowire, indicating that it has an out-of-plane anisotropy at both sites, whilst the Co and Ni nanowire show an in-plane anisotropy. Recent ab initio studies of Fe double chains on Ir (001) surface [12,13] show that the anisotropy could be either in-plane or out of plane, depending on the inter-chain distance and the magnetic configuration of the chain. The MAEs of the freestanding 3d TM atomic chains [14] were already obtained by the force theorem method with a fine 1×1×n (n = 200) k-point mesh, and the calculated MAE E 1 was -2.25, 0.68 and -8.13 (meV/mag.…”

Noncollinear magnetism in freestanding and supported monatomic Mn chains

“…Such a correspondence between the direction of the atomic spin moment in the deposited chain and the vacuum magnetization was also found for biatomic Fe chains on an Ir substrate. 10 Now we turn to the calculated spin-polarized STM images which have been obtained applying the spin-polarized version of the Tersoff-Hamann model 55 and using the electronic structure calculated within DFT. Figure 10 displays the result for a tip magnetization along the y direction.…”

“…While the exchange interactions have been explored intensively for finite TM magnetic clusters, both freestanding and deposited on surfaces, 9,17-20 the work for infinite monatomic TM chains concentrated almost exclusively on collinear magnetic solutions. 10,[21][22][23][24][25][26] The occurrence of noncollinear magnetic states and analysis of exchange interaction beyond the first neighbor in freestanding and deposited monatomic chains has come into the focus of interest only recently, [27][28][29] while a conclusive evidence for a spin-spiral ground state, or more complicated spin textures, The E and q axes have been added for one curve for clarity (lower right corner of right graph). In that particular case, the global energy minimum is at the end; that is, for q = 0.5 and the AFM state is most favorable.…”

“…1,5,7 Owing to the rich physics in 1D systems many more novel effects and phenomena have been reported in the recent years concerning their electronic structure, spin dynamics, and transport properties. 3,[8][9][10][11][12][13] The creation of monatomic chains in experiment is extremely challenging; however, in the most recent years, a few techniques to achieve this goal have been successfully developed. One experimental approach is the formation of chains in so-called mechanically controllable break junctions.…”

Quantum theory of spin waves in finite chiral spin chains

“…1). This system [13] has attracted interest both because of the nontrivial interplay between structure and magnetic coupling [14,15] and because a local perturbation in one side of the chain affects the spin state globally, as a consequence of long range spin order [16], as in the case of antiferromagnetically coupled spin chains [3]. The robustness of spin spiral states against formation of domain walls is also considered an advantage [4].…”