Correlation between Electronic Configuration and Magnetic Stability in Dysprosium Single Atom Magnets

Abstract

Single atom magnets offer the possibility of magnetic information storage in the most fundamental unit of matter. Identifying the parameters that control the stability of their magnetic states is crucial to design novel quantum magnets with tailored properties. Here we use X-ray absorption spectroscopy to show that the electronic configuration of dysprosium atoms on MgO(100) thin films can be tuned by the proximity of the metal Ag(100) substrate onto which the MgO films are grown. Increasing the MgO thickness from 2.5 to 9 monolayers induces a change in the dysprosium electronic configuration from 4f 9 to 4f 10 . Hysteresis loops indicate long magnetic lifetimes for both configurations, however, with a different field-dependent magnetic stability. Combining these measurements with scanning tunneling microscopy, density functional theory, and multiplet calculations unveils the role of the adsorption site and charge transfer to the substrate in determining the stability of quantum states in dysprosium single atom magnets.

Slow Magnetic Relaxation of Dy Adatoms with In-Plane Magnetic Anisotropy on a Two-Dimensional Electron Gas

“…Very similar results are obtained for Dy adsorbed on the (001) surface of pure (i.e., without Nb doping) STO (see Supporting Information for a comparison between pure and Nb-doped STO), indicating that the extra conductivity achieved through Nb doping does not shorten the magnetization relaxation times. Dy/STO(001) can therefore be classified as a SAM, but unlike the previously reported cases of RE SAMs, 14,21,22,50 all showing strong out-of-plane magnetic anisotropy, here the Dy atoms have in-plane magnetic anisotropy. Contrary to Dy, Ho single atoms show purely paramagnetic behavior down to T = 2.5 K, despite a magnetic anisotropy similar to that of Dy (see Supporting Information for the Ho/STO magnetic properties).…”

Emerging Trends on Designing High-Performance Dysprosium(III) Single-Molecule Magnets

“…Inversely, the equatorial CF is preferable for Er­(III) ion where two representative complexes, that is, [Dy­(Cp ttt ) 2 ] + , and Er­[N­(SiMe 3 ) 2 ] 3 , are provided as an illustrative example. Apart from the molecular origin, the assembling of individual lanthanide atoms on surfaces for single-atom magnetic recording has also been developed in recent years, representing the ultimate limit of high-density storage devices. − …”

Metamagnetic transition and a loss of magnetic hysteresis caused by electron trapping in monolayers of single-molecule magnet Tb2@C79N

“…100 Coexistence of Dy atoms and Dy + ions with the ratio depending on the MgO thickness was recently demonstrated for Dy deposited on MgO|Ag(100). 104 Such situations are less documented for adsorbates on h-BN|metal substrates, 105 but not unimaginable either. For instance, C 60 retains its charge state on h-BN|Ni(111) at low temperature, but the population of its LUMO is increased by 0.4 electrons at room temperature.…”

“…The persistence of the afm state on h-BN| Rh (111) and MgO|Ag(100) could serve as an indication that the charge transfer from the substrate is not the reason for the unexpected magnetic behavior of Tb 2 @C 79 N. However, the charge transfer hypothesis still cannot be fully excluded by these data because there are examples of the electron transfer between Ag and adsorbate on MgO|Ag(100) substrates. [98][99][100][101][102][103][104] For instance, pentacene molecules acquire one electron when deposited onto MgO(2 ML)|Ag (100). 99 Variation of the MgO layer thickness and work-function resulted in the co-existence of neutral and charged pentacene molecules, and signatures of the charge transfer were observed up to the MgO thickness of 16 ML.…”