Kondo effect and enhanced magnetic properties in gadolinium functionalized carbon nanotube supramolecular complex

Abstract

We report on the enhancement of magnetic properties of multiwalled carbon nanotubes (MWNTs) functionalized with a gadolinium based supramolecular complex. By employing a newly developed synthesis technique we find that the functionalization method of the nanocomposite enhances the strength of magnetic interaction leading to a large effective moment of 15.79 µB and non-superparamagnetic behaviour unlike what has been previously reported. Saturating resistance at low temperatures is fitted with the numerical renormalization group formula verifying the Kondo effect for magnetic impurities on a metallic electron system. Magnetoresistance shows devices fabricated from aligned gadolinium functionalized MWNTs (Gd-Fctn-MWNTs) exhibit spin-valve switching behaviour of up to 8%. This study highlights the possibility of enhancing magnetic interactions in carbon systems through chemical modification, moreover we demonstrate the rich physics that might be useful for developing spin based quantum computing elements based on one-dimensional (1D) channels.

Tuning Magnetic Properties of a Carbon Nanotube-Lanthanide Hybrid Molecular Complex through Controlled Functionalization

“…As shown in Figure 6b, we determine Kondo onset temperatures (T K ) [31,32] of 132, 155, 188 and 202 K as a function on increasing Gd concentration. These findings are in agreement with the analysis of the Raman deconvolution study and shed light onto how structural degradation and magnetic loading can lead to enhanced spin correlations in functionalized carbon systems as recently demonstrated through the observation of the impurity Kondo effect [33][34][35]. Furthermore, these findings are significant as they help explain the role of itinerate electrons in mediating the interaction between spatially separated spin centers and thus may provide a mechanism for tuning the system from a superparamagnetic material to a highly correlated system with a definite spin texture.…”

Structure of inorganic nanocrystals confined within carbon nanotubes

“…In the case of iron oxide, superparamagnetic nanowires were stabilized within DWCNTs [73], also leading to magneto-Coulomb effects [74]. DWCNTs Filled with Gadolinium exhibited Kondo effect and enhanced magnetic properties [75,76].…”

Interaction of Luminescent Defects in Carbon Nanotubes with Covalently Attached Stable Organic Radicals

“…Previously, mixed-chirality samples of SWCNTs and multiwalled carbon nanotubes were decorated with open-shell transition metal 18 or lanthanide 19,20 complexes, and charge transport measurements at cryogenic temperatures revealed spin valve switching behavior without the need for ferromagnetic contacts. 19,20 Another class of spin-bearing compounds are stable organic radicals, i.e., charge-neutral molecules with an unpaired electron. 21,22 One of the most prominent examples is the perchlorinated triphenylmethyl (PTM) radical, in which a propeller-shaped arrangement of phenyl rings protects the carbon-centered radical, resulting in a half-life of ∼100 years.…”

“…A highly desirable property for functional groups attached to SWCNTs is a net spin, as carried by unpaired electrons. Previously, mixed-chirality samples of SWCNTs and multiwalled carbon nanotubes were decorated with open-shell transition metal or lanthanide , complexes, and charge transport measurements at cryogenic temperatures revealed spin valve switching behavior without the need for ferromagnetic contacts. , Another class of spin-bearing compounds are stable organic radicals, i . e ., charge-neutral molecules with an unpaired electron. , One of the most prominent examples is the perchlorinated triphenylmethyl (PTM) radical, in which a propeller-shaped arrangement of phenyl rings protects the carbon-centered radical, resulting in a half-life of ∼100 years .…”