Exceptionally High Blocking Temperature of 17 K in a Surface‐Supported Molecular Magnet

Abstract

liquid-nitrogen temperature [3] or single atoms exhibiting extremely long magnetic relaxation times. [4][5][6] In particular, systems based on late lanthanide family elements, like Dy and Tb, have been largely in focus, including single-molecule, [2,3] singleatom, [4,5] or single-chain magnets. [7,8] Adsorption of SMMs on surfaces allows to study individual molecular units, as well as to realize transport schemes essential for the implementation of SMMs in molecular-scale spintronics or quantum computing devices. [9][10][11][12][13][14][15][16][17] However the transition from bulk to surface-supported systems often goes along with a substantial change or even loss of SMM properties, that is, magnetic moment, magnetic anisotropy, or magnetization behavior. [18][19][20][21] On metallic surfaces, the interaction of the magnetic moments with the surface is rather strong, which is evidenced by the observation of the Kondo effect. [22,23] Thus, benchmark measurements during the last years demonstrating magnetic bistability of surface-adsorbed SMMs have been reported on substrates, where molecules are electronically weakly coupled to -TbPc 2 on HOPG, [24] on MgO/Ag(100) [25] and on graphene/SiC, [26] pushing the blocking temperature (T B ) limit up to 9 K. On the other hand, DySc 2 N@C 80 monolayers on Au(111) [27] recently showed a hysteresis opening at temperatures up to 10 K. In this sense, lanthanide ions encaged in C 80 molecules reportedly outperform most SMMs by their combination of chemical robustness with slow magnetic relaxation. [27][28][29][30][31] To further push the magnetic lifetime in the monolayer regime two important criteria have to be fulfilled: the first requirement is to synthesize SMM compounds showing intrinsically high T B in the bulk. The second requires implementation of the appropriate methods for molecular deposition on substrates, which provide sufficient decoupling of the SMM from the surface.In this work we provide experimental evidence on outstanding slow magnetic relaxation in Dy 2 @C 80 (CH 2 Ph) sub-monolayers on a graphene/Ir(111) surface. The Dy 2 @C 80 (CH 2 Ph) molecules deposited by the electrospray deposition method are organized into islands as shown by low-temperature scanning tunneling microscopy (STM) imaging. We explore their magnetic properties by means of X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements. The analysis of the magnetic relaxation behavior of Dy 2 @C 80 (CH 2 Ph) adsorbed on graphene/Ir(111) yields a Single-molecule magnets (SMMs) are among the most promising building blocks for future magnetic data storage or quantum computing applications, owing to magnetic bistability and long magnetic relaxation times. The practical device integration requires realization of 2D surface assemblies of SMMs, where each magnetic unit shows magnetic relaxation being sufficiently slow at application-relevant temperatures. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism, it is shown that sub-monolayers of Dy ...

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

“…S16 in ESI†). This proves that the X-ray irradiation considerably accelerates magnetic relaxation in Tb 2 @C 79 N. Such X-ray induced demagnetization was reported earlier in monolayers of metallofullerenes 61,62,96 and TbPc 2 , 46 but the effect in Tb 2 @C 79 N is more pronounced. Further measurements of (sub)monolayer films demonstrate that not only the demagnetization rate but also the population of valence orbitals may be affected by X-ray irradiation through secondary processes.…”

“…[56][57][58][59][60][61][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. [56][57][58][59][60] _ENREF_71_ENREF_73 Even more promising are recent studies of Dy 2 @C 80 (CH 2 Ph) deposited onto graphene 61 and Tb 2 @C 80 (CH 2 Ph) on graphene and HOPG, 62 which demonstrated that dimetallofullerenes with single-electron lanthanidelanthanide bonds can also sustain their superb SMM performance in monolayers. Magnetic hysteresis in these monolayers was observed at considerably higher temperatures than in all other surface-supported SMMs, reaching 28 K for a self-assembled monolayer of Tb 2 @C 80 (CH 2 Ph) derivative.…”

“…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. 56–60 Even more promising are recent studies of Dy 2 @C 80 (CH 2 Ph) deposited onto graphene 61 and Tb 2 @C 80 (CH 2 Ph) on graphene and HOPG, 62 which demonstrated that dimetallofullerenes with single-electron lanthanide–lanthanide bonds can also sustain their superb SMM performance in monolayers.…”

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

“…Recently, Fonin and co-workers were able to preserve the reported magnetic remanence of Dy 2 @C 80 (CH 2 Ph) on the graphene/Ir(111) surface exhibiting T B of 17 K at the field sweep rate of 2 T min −1 . 53 The integrating of SMM with hybrid materials usually diminishes its magnetic performance due to the formation of buffer environment between the substrate and magnetic materials; however, in this report, they were able to preserve magnetic remanence comparable with the original bulk system. 103 In addition, the utilization of paramagnetic bridging radical ligands enabling the establishment of strong magnetic coupling between the lanthanide centers under constrained coordination environments is becoming another successful strategy.…”

Electrophilic Trifluoromethylation of Dimetallofullerene Anions en Route to Air-Stable Single-Molecule Magnets with High Blocking Temperature of Magnetization

“…Even slight overheating changes its mechanism from nucleophilic substitution to radical polyaddition, which produces intractable mixtures of EMF­(CH 2 Ph) n multiadducts. As di-EMFs with single-electron lanthanide–lanthanide bond are very robust SMMs and qubit candidates, ,,,− development of a streamlined approach to their synthesis and separation would be very beneficial.…”