Engineering Chemisorption of Fe₄ Single‐Molecule Magnets on Gold

Abstract

Gaining control over the grafting geometry is critically important for any application of surface‐supported single‐molecule magnets (SMMs) in data storage, spintronics, and quantum information science. Here, tetrairon(III) SMMs with a propeller‐like structure are functionalized with thioacetyl‐terminated alkyl chains to promote chemisorption on gold surfaces from solution and to evaluate differences in adsorption geometry and magnetic properties as a function of chain length. The prepared monolayers are investigated using X‐ray absorption techniques with linearly and circularly polarized light to extract geometrical and magnetic information, respectively. All derivatives remain intact and form partially oriented monolayers on the gold surface. A ligand‐field analysis of the observed X‐ray natural linear dichroism shows that the threefold molecular axis is invariably biased toward the surface normal, in agreement with ab initio calculations. This preferential orientation is most pronounced in monolayers of the shortest‐chain derivative, which are further studied with an ultralow temperature X‐ray magnetic circular dichroism setup operating down to 350 mK. The isothermal field sweeps with the magnetic field at normal incidence show an open hysteresis loop below 1 K, while measurements at different incidence angles prove the magnetic anisotropy of the monolayers.

Electronic and Magnetic Properties of a Monolayer of VOTPP Molecules Sublimated on Ag(100)

“…The information about the molecular orientation on the Ag surface was inferred by the XNLD (𝜎 V -𝜎 H ) signal obtained by collecting XAS spectra with vertical (𝜎 V ) and horizontal polarized light (𝜎 H ) as reported in Figure 3a. [10,11,[39][40][41][42] The XNLD spectrum shows a significant dichroic signal at the L 2,3 edges of V (more than 30%), suggesting that the PM leans down preferentially toward the Ag(100) surface. [10,11,43] For the sake of completeness we performed XNLD characaterization also at a very low magnetic field (0.02T) to exclude the presence of an X-ray Magnetic Linear Dichroism (XMLD) contribution (see Figure S3, Supporting Information).…”

Challenges for exploiting nanomagnet properties on surfaces

“…For SMMs, hysteresis temperatures are compared. For qubits, relaxation times are compared SMM T Hysteresis (bulk) Surface Hysteresis on surface T Hysteresis (on-surface) Reference TbPc 7 K MgO/Ag(100) Yes 3 K 29 Ag(100) No – HOPG Yes 7 K 47 Au(111) Yes 15 K (200 nm film) 4.5 K (monolayer) 46 Fe 4 < 1 K Au(111) Yes 0.9 K 72 Au(111) Yes 0.7 K 22 Au(111) Yes 0.65 K 119 Dy 12 < 1 K IONPs Yes 30 K* 28 (Cp) ttt 2 DyCl < 2 K SiO2 particles Yes 8 K 39 Dy 2 @C 80 (CH 2 Ph) 20 K graphene/Ir(111) Yes 20 K 48 * synergistic effect with IONP, hysteresis of pristine IONP at 10 K Qubit T 1 and/or T 2 Bulk Surface T 1 and/or T 2 on-surface Reference [Cu(dttt) 2 ] T 2 = 2.3 µs Kapton No 81 TEMPO r...…”

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

“…Sustained magnetic bistability in a thin film, a monolayer, and eventually a single molecule in contact with a conducting substrate is an important prerequisite for the use of SMMs in nanoscale spintronics. However, a realization of hysteretic behaviour in monolayers is not straightforward and was demonstrated only for a handful of SMMs, 35–55 including some metallofullerene-SMMs. 56–62 The nitride clusterfullerenes Dy 2 ScN@C 80 and DySc 2 N@C 80 were shown to maintain their SMM properties in monolayers on metallic substrates.…”