Quantifying exchange forces of a spin spiral on the atomic scale

Abstract

We quantify the atomic-scale variation of the magnetic exchange force field between a ferromagnetic tip and the cycloidal spin spiral of one monolayer Mn on the W(110) surface, by utilizing the combination of spin-polarized scanning tunneling microscopy and magnetic exchange force microscopy (SPEX). Compared to the surprisingly weak spin polarization, the exchange force field is more sensitive to atomic-scale variations in the magnetization. First-principles calculations reveal that the measured atomic-scale variations in the exchange force originate from different contributions of direct and indirect (Zener) type exchange mechanisms, depending on the chemical tip termination. The weak spin polarization of the tunneling current results from pz states which dominate the local density of states around the Fermi energy. Our work provides the first characterization of the exchange force field together with the spin polarization of a spin spiral and opens the perspective of quantifying different exchange mechanisms of chiral magnetic structures with atomic-scale precision.

Electronic and magnetic properties of 3d transition-metal adatoms on Mn/W(110)

“…At the respective positions of the local maxima, the spin polarization takes on values ranging from 74% up to 84%, while the effect is slightly smaller at E F with a value of 55%. However, this value is still nearly three times higher than the one of 20% which has recently been reported for the clean Mn/W(110) surface 21 . As already shown in Table II, a Mn atom in the monolayer on the W(110) substrate exhibits a large spin moment of 3.41 µ B thereby causing a large exchange splitting of the 3d bands which are shifted away from E F .…”

“…Thereby, the transport properties of magnetic adatoms as a function of spin direction can be probed using spin-polarized scanning tunneling microscopy (SP-STM) [17][18][19] . Recently, even a simultaneous measurement of the spin-polarized tunneling current and of the local exchange force between a magnetic tip and a surface with a noncollinear spin structure has been obtained 20,21 .…”

First‐principles study of the magnetic exchange forces between the RuO2(110) surface and Fe tip

“…Positive and negative signs for E ex z ð Þ correspond to preferential p and ap coupling, respectively. Similarly, the exchange force F ex is defined as [21,33]…”

Minimally invasive spin sensing with scanning tunneling microscopy

“…This has to be taken into special consideration when trying to harness their magnetic states for data storage, 7,8 spintronics 8 and quantum devices. [8][9][10] Scanning probe microscopy has become an essential tool 11 for probing magnetic surfaces, [12][13][14] atoms, 4,[15][16][17][18] atom chains, 19,20 and molecules. [21][22][23][24][25][26][27][28] All scanning probe techniques irrespective of whether they use magnetic forces or spinpolarized current for detectionrequire the presence of a local probe tip.…”

“…[21][22][23][24][25][26][27][28] All scanning probe techniques irrespective of whether they use magnetic forces or spinpolarized current for detectionrequire the presence of a local probe tip. Its proximity can perturb the investigated object, through mechanical interaction, [29][30][31][32] magnetic stray field, 33 electric fields, 23,29,[34][35][36][37] magnetic exchange coupling 12,14,38 as well as electron injection. 7,39 Whereas magnetic force and magnetic exchange force microscopy have been used to great effect for the investigation of extended magnetic surfaces without the use of electric current, the majority of atomic-scale magnetic structures have been studied with STM where the impact of the tunneling electrons must be considered.…”