Carbon Nanotube Nanoelectromechanical Systems as Magnetometers for Single-Molecule Magnets (original) (raw)
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Nature Nanotechnology, 2013
Magnetic relaxation processes were first discussed for a crystal of paramagnetic transition ions 1 . It was suggested that mechanical vibrations of the crystal lattice (phonons) modulate the crystal electric field of the magnetic ion, thus inducing a 'direct' relaxation between two different spin states 1-3 . Direct relaxation has also been predicted for single-molecule magnets with a large spin and a high magnetic anisotropy and was first demonstrated in a Mn 12 acetate crystal 8 . The spin-lattice relaxation time for such a direct transition is limited by the phonon density of states at the spin resonance 1 . In a three-dimensional system, such as a single-molecule magnet crystal, the phonon energy spectrum is continuous, but in a one-dimensional system, like a suspended carbon nanotube, the spectrum is discrete and can be engineered to an extremely low density of states 9 . An individual single-molecule magnet, coupled to a suspended carbon nanotube, should therefore exhibit extremely long relaxation times 9 and the system's reduced size should result in a strong spin-phonon coupling 10,11 . Here, we provide the first experimental evidence for a strong spin-phonon coupling between a single molecule spin and a carbon nanotube resonator, ultimately enabling coherent spin manipulation and quantum entanglement 10,11 .
Anchoring of Rare-Earth-Based Single-Molecule Magnets on Single-Walled Carbon Nanotubes
Journal of the American Chemical Society, 2009
A new heteroleptic bis(phthalocyaninato) terbium(III) complex 1, bearing a pyrenyl group, exhibits temperature and frequency dependence of ac magnetic susceptibility, typical of single-molecule magnets. The complex was successfully attached to single-walled carbon nanotubes (SWNTs) using π-π interactions, yielding a 1-SWNT conjugate. The supramolecular grafting of 1 to SWNTs was proven qualitatively and quantitatively by high-resolution transmission electron microscopy, emission spectroscopy, and atomic force spectroscopy. Giving a clear magnetic fingerprint, the anisotropy energy barrier and the magnetic relaxation time of the 1-SWNT conjugate are both increased in comparison with the pure crystalline compound 1, likely due to the suppression of intermolecular interactions. The obtained results propose the 1-SWNT conjugate as a promising constituent unit in magnetic single-molecule measurements using molecular spintronics devices.
International Journal of Molecular Sciences, 2011
We built new hybrid devices consisting of chemical vapor deposition (CVD) grown carbon nanotube (CNT) transistors, decorated with TbPc 2 (Pc = phthalocyanine) rare-earth based single-molecule magnets (SMMs). The drafting was achieved by tailoring supramolecular π-π interactions between CNTs and SMMs. The magnetoresistance hysteresis loop measurements revealed steep steps, which we can relate to the magnetization reversal of individual SMMs. Indeed, we established that the electronic transport properties of these devices depend strongly on the relative magnetization orientations of the grafted SMMs. The SMMs are playing the role of localized spin polarizer and analyzer on the CNT electronic conducting channel. As a result, we measured magneto-resistance ratios up to several hundred percent. We used this spin valve effect to confirm the strong uniaxial anisotropy and the superparamagnetic blocking temperature (T B ~ 1 K) of isolated TbPc 2 SMMs. For the first time, the strength of exchange interaction between the different SMMs of the molecular spin valve geometry could be determined.
Carbon nanotube based magnetic flux detector for molecular spintronics
physica status solidi (b), 2007
This work describes the study of a superconducting quantum interference device (SQUID) with singlewalled carbon nanotube (CNT) Josephson junctions. Quantum confinement in each junction induces a discrete quantum dot (QD) energy level structure, which can be controlled with two lateral electrostatic gates. The gates are also used to directly tune the quantum phase interference of the Cooper pairs circulating in the SQUID ring. Optimal modulation of the switching current with magnetic flux is achieved when both QD junctions are in the 'on' or 'off' state. In particular, the SQUID design establishes that these CNT Josephson junctions can be used as gate-controlled π junctions. Besides, the CNT-SQUIDs are sensitive local magnetometers, which are very promising for the study of magnetization reversal of an individual magnetic particle or molecule placed on one of the two CNT Josephson junctions.
Towards molecular spintronics: magnetotransport and magnetism in carbon nanotube-based systems
Diamond and Related Materials, 2003
We describe first approaches towards a carbon nanotube (CNT) based spintronics. The building blocks consist of pristine multiwall CNTs and metallic ferromagnetic electrodes. The devices exhibit magnetoresistive effects up to several 10% at 4.2 K the origin of which is tentatively attributed to spin-dependent tunneling through an insulating barrier between the CNT and the electrode. We also show results of filling multi-wall CNTs with ferromagnetic materials. These magnetic quantum wires are fascinating objects in itself, revealing unusual magnetic properties. They may also be used, however, as magnetic electrodes to contact to the innermost shell of the nanotube in future molecular spintronics devices. ᮊ
Single-Walled Carbon Nanotubes for a Strain-based Magnetometer
2006 Sixth IEEE Conference on Nanotechnology, 2006
A design for a single-walled carbon nanotube (SWCNT) magnetometer will be presented. The operating II. METHODOLOGY principle exploits the sensitivity of SWCNT electrical properties The SWCNT magnetometer design consists of three major to strain. The sensor design consists of a free-standing mat of components: a free-staniding mat of SWCNTs, a suspended SWCNTs that is mechanically coupled to a magnetically lage aspect-rio Fe needle and a set of electrodes. A responsive, high aspect-ratio Fe component. During operation, schem atio Fie 1. Piary der of e thsdesign torque on the Fe needle will transduce ambient magnetic field schematr c iS shorin sr F cgure1aPlruar drivers of this d, tih strength into an electronic signal. Prelinminary results of aredevice redition atstcturalsrongsttess. etion, the precursor SWCNT material will be presented, including theoretical prediction that die strongest electroinechafiical magneticu ield-and temperature-depenence of electron response is associated with small band gap semiconducting transpert measurements, and implications fr magneitometer SWCNTs [2] demands that an ensemble be used to account for operation wuill bee discussed. the dispersion in electronic properties characteristic of CVDgrown SWCNTs and for reproducibility in fabrication.
Magnetism of Covalently Functionalized Carbon Nanotubes
2011
We investigate the electronic structure of carbon nanotubes functionalized by adsorbates anchored with single C-C covalent bonds. We find that, despite the particular adsorbate, a spin moment with a universal value of 1.0 muB\mu_BmuB per molecule is induced at low coverage. Therefore, we propose a mechanism of bonding-induced magnetism at the carbon surface. The adsorption of a single molecule creates a dispersionless defect state at the Fermi energy, which is mainly localized in the carbon wall and presents a small contribution from the adsorbate. This universal spin moment is fairly independent of the coverage as long as all the molecules occupy the same graphenic sublattice. The magnetic coupling between adsorbates is also studied and reveals a key dependence on the graphenic sublattice adsorption site.
Advanced Materials, 2007
The determination of the magnetic properties of molecular magnets in environments similar to those used in spintronic devices is fundamental for the development of applications. Single-molecule magnets (SMMs) are molecular cluster systems that display magnetic hysteresis of dynamical origin at low temperature. As they behave like perfectly monodisperse nanomagnets and show clear macroscopic quantum effects in their magnetic properties, they are extremely appealing candidates for the forthcoming generation of molecular devices: they have been proposed as efficient systems for quantum computation, ultra-high-density magnetic recording media, and molecular spintronic systems. These attractive possibilities have stimulated the creativity of chemists and materials scientists in developing several different ways of organizing such systems into addressable nanostructured materials. In particular inclusion into Langmuir-Blodgett (LB) films, [9] mesoporous silica, polymeric matrices, and ultrathin films [12] have been devised and studied. The most appealing approaches, both from the applicative and speculative points of view, are the functionalization and binding of such clusters on conducting surfaces as well as their incorporation into break-junctions, where a single molecule is directly accessible. These results have led to the creation of the first SMM-based molecular spintronic devices, in which the electronic transport properties are modulated by the magnetic state of a single SMM cluster. The considerable difficulties linked to the interpretation of such results have recently stimulated much theoretical work, and a number of predictions have been made. Both topological and quantum tunneling effects on the transport in the Kondo regime have been predicted, and several peculiar fingerprints of the SMM behavior should be apparent in transport measurements. Interesting effects are also predicted when addressing a SMM on a surface with a tunneling current. Although the influence of the surroundings on the magnetic properties of SMMs has been pointed out in several theoretical and experimental works, our understanding of SMM behavior almost totally relies on measurements performed on crystalline samples. Magnetic measurements on SMMs that lie in environments similar to those of spintronic devices have not been reported up to now, mainly because of the very high sensitivity required. In this Communication we try to fill this void by using high-sensitivity instrumentation, based on magneto-optical (MO) techniques on a variety of materials.
Magnetic Interaction Between a Radical Spin and a Single-Molecule Magnet in a Molecular Spin-Valve
ACS nano, 2015
Molecular spintronics using single molecule magnets (SMMs) is a fast growing field of nanoscience that proposes to manipulate the magnetic and quantum information stored in these molecules. Herein we report evidence of a strong magnetic coupling between a metallic ion and a radical spin in one of the most extensively studied SMMs: the bis(phtalocyaninato)terbium(III) complex (TbPc2). For that we use an original multi-terminal device comprising a carbon nanotube laterally coupled to the SMMs. The current through the device, sensitive to magnetic interactions, is used to probe the magnetization of a single Tb ion. Combining this electronic read-out with the transverse field technique has allowed us to measure the interaction between the terbium ion, its nuclear spin and a single electron located in the phtalocyanines ligands. We show that the coupling between the Tb and the ligand radical is strong enough to give extra resonances in the hysteresis loop that are not observed in the ani...