Spin-state-dependent electrical conductivity in single-walled carbon nanotubes encapsulating spin-crossover molecules

Abstract

Spin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.

Spin-crossover complexes in nanoscale devices: main ingredients of the molecule–substrate interactions

“…In all calculations the SWCNT is a (16,8) nanotube with a diameter of 1.65 nm and a unit cell of 224 carbon atoms. This chirality corresponds to a semiconductor, in agreement with the transport measurements of the bare SWCNT, 42 while the relatively reduced size of the unit cell enables the complete optimization of both the SCO complex and the nanotube.…”

“…Recently we have reported for the first time the encapsulation of Fe(II) spin-crossover complexes in single-walled carbon nanotubes. 42 Two Fe(II) SCO complexes with the formula [Fe (H 2 Bpz 2 ) 2 (L)] were studied, with H 2 Bpz 2 = dihydrobis( pyrazolyl)borate and L = 1,10-phenanthroline ( phen, SCO1) or 2,2′bipyridine (bipy, SCO2) (Fig. 1a).…”

“…1a and b). 42 Conductance through the host nanotube showed a distinct bistability associated with the spin state of the guest SCO molecules. A conductance hysteresis not present in the magnetism of macroscopic crystals was reported as a consequence of the particular conditions that molecules experience at the nanoscale (Fig.…”

Statistical analysis of spin switching in coupled spin-crossover molecules

“…Both mechanicallyand electrically-induced spin state switching has been observed in mechanically controllable break junctions (MCBJs), while electromigrated nanogap devices have also demonstrated gate-controlled spin switching [21][22][23]. In addition to this, spin crossover complexes coupled to graphene-based devices have been investigated in an effort to reduce surface interactions, which adversely effect the switching properties [24,25].…”

Capture of Fullerenes in Cages and Rings by Forming Metal-π Bond Arene Interactions

“…In this sense, the confinement of fullerenes has led to structures [ 16 ] with different features, such as photosensitization [ 17 ]. They can be used to tune conductivity of MOFs [ 18 ], to develop supramolecular architectures [ 19 ] and electric and magnetic nano switches [ 20 ]. The present work deals in part with this problem, the long-range interaction of fullerene with different systems carrying electron rich centers is theoretically analyzed.…”