Molecular magnets attached to carbon nanotubes (CNT) are being studied as potential candidates for developing spintronic and quantum technologies. However, the functionalization routes used to develop these hybrid systems can drastically affect their respective physiochemical properties. Due to the complexity of this systems, little work has been directed at establishing the correlation between the degree of functionalization and the magnetic character. Here, we demonstrate the chemical functionalization degree associated with molecular magnet loading can be utilized for controlled tuning the magnetic properties of a CNT-lanthanide hybrid complex. CNT functionalization degree was evaluated by interpreting minor Raman phonon modes in relation to the controlled reaction conditions. These findings were exploited in attaching a rare-earth-based molecular magnet (Gd-DTPA) to the CNTs. Inductively coupled plasma mass spectrometry, time-of-flight secondary ion mass spectrometry and super conducting quantum interference device (SQUID) measurements were used to elucidate the variation of magnetic character across the samples. This controlled Gd-DTPA loading on the CNT surface has led to a significant change in the nanotube intrinsic diamagnetism, showing antiferromagnetic coupling with increase in the Weiss temperature with respect to increased loading. This indicates that synthesis of a highly correlated spin system for developing novel spintronic technologies can be realized through a carbon-based hybrid material.
This study is focused on a bottom-up nano-integration route for the production of carbon based spintronic devices. In order to enhance magnetic interactions along nanotube walls a controlled synthetic chemical technique is utilized, this method is based on a two-step method which firstly looks at the functionalization of nanotubes (carbonyl groups) and subsequently the attachment of an organo-metallic complex to the carbonyl group. The system is then characterized in bulk, including magnetometry analysis as well as transport at low temperatures. Mesoscopic electron-spin correlations have been observed as well as a clear crossover from superparamagnetism to weakly ferromagnetic depending on the functionalization technique. We then demonstrate a novel fabrication technique based on nano-integration utilizing a nano-tweezer created from a memory metal alloy. The devices envisioned include quantum rings, crossed junction as well as fine network structures that can be manipulated using nano-probes. As the carbon nanotubes have been functionalized with nanoscale magnetic molecules, such devices are interesting for novel spintronic applications.
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