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Structural evolution and magnetic properties of underfluorinated C2F
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
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2012 (English)In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, Vol. 25, no 1, 79-83 p.Article in journal (Refereed) Published
Abstract [en]

A series of layered inclusion compounds based on fluorinated graphite C2F x (x≤1) was obtained by a room temperature synthesis. Inclusion compounds (intercalates) of fluorinated graphite matrix were n-hexane and dichloromethane, i.e., organic guest molecules that differ in size and symmetry. The changes in C2F x stoichiometry are shown to have a decisive effect on magnetic properties of produced complexes. The spin concentration decreases with the increase of fluorine content in fluorocarbon matrix. All samples have groups of correlated spins; at the temperatures 1.75–5 K nonlinear magnetization is observed, indicating a high-spin state. Application of the Langevin formula shows that the clusters consist of 10–20 interacting spins.

Place, publisher, year, edition, pages
Springer , 2012. Vol. 25, no 1, 79-83 p.
Keyword [en]
Graphite fluoride, Magnetic properties, X-ray diffraction, Infrared spectroscopy
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:umu:diva-45911DOI: 10.1007/s10948-011-1209-2OAI: oai:DiVA.org:umu-45911DiVA: diva2:435815
Available from: 2011-08-20 Created: 2011-08-20 Last updated: 2012-05-23Bibliographically approved
In thesis
1. Carbon-based magnetic nanomaterials
Open this publication in new window or tab >>Carbon-based magnetic nanomaterials
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Magnetism of carbon-based materials is a challenging area for both fundamental research and possible applications. We present studies of low-dimensional carbon-based magnetic systems (fullerene-diluted molecular magnets, carbon nanotubes, graphite fluoride, and nanoporous carbon) by means of SQUID magnetometer, X-ray diffraction and vibrational spectroscopy, the latter techniques used as complementary instruments to find a correlation between the magnetic behaviour and the structure of the samples.In the first part of the thesis, characteristic features of the magnetization process in aligned films of carbon nanotubes with low concentration of iron are discussed. It is shown that the magnetism of such structures is influenced by quantum effects, and the anisotropy behaviour is opposite to what is observed in heavily doped nanotubes.In the second part, Mn12-based single molecular magnets with various carboxylic ligands and their 1:1 fullerene-diluted complexes are studied. We prove that magnetic properties of such systems strongly depend on the environment, and, in principle, it is possible to design a magnet with desirable properties. One of the studied compounds demonstrated a record blocking temperature for a single molecular magnet. Both fullerene-diluted complexes demonstrated “magnetization training” effect in alternating magnetic fields and the ability to preserve magnetic moment.The third and the fourth parts of the thesis are dedicated to the analysis of various contributions to the magnetic susceptibility of metal-free carbon-based systems – intercalated compounds of graphite fluorides and nanoporous oxygen-eroded graphite. The magnetic properties of these systems are strongly dependent on structure, and can be delicately tuned by altering the π-electron system of graphite, i. e. by degree of fluorination of intercalated compounds and by introduction of boron impurity to the host matrix of nanoporous graphite.

Abstract [sv]

Magnetism av kolbaserade material är ett utmanande område för både grundforskning och möjliga tillämpningar.

Vi presenterar studier med låg-dimensionella kolbaserade magnetiska system (fulleren-utspädda molekylära magneter, kolnanorör, grafit fluorid och nanoporösa kol) med hjälp av SQUID magnetometer, röntgendiffraktion och vibrerande spektroskopi, de senare tekniker som används som komplement instrument för att finna sambandet mellan den magnetiska uppträdande och strukturen hos proven.

I den första delen av avhandlingen är egenheter från magnetisering processen i linje filmer av kolnanorör med låg koncentration av järn diskuteras. Det visas att magnetism av sådana strukturer påverkas av kvantmekaniska effekter och anisotropin beteende är motsatsen till vad som observerats i kraftigt dopade nanorör.

I den tvåa delen är Mn12-baserade enda-molekyl magneter med olika karboxylsyror ligander och deras 1:1 fulleren-utspädda komplex studeras. Vi visar att magnetiska egenskaperna hos sådana system beror i hög grad på miljön, och i princip är det möjligt att utforma en magnet med önskvärda egenskaper. En av de studerade föreningarna visade en post blockeringstemperaturen för en enda molekylär magnet. Både fulleren-utspädda komplex visade "magnetisering utbildning" effekt i alternerande magnetfält och möjligheten att bevara magnetiskt moment.

Den tredje och fjärde delarna av avhandlingen är avsedda för inneboende magnetism av analys av olika bidrag till magnetisk susceptibilitet av metall-fritt kol-baserade system -inskjutna föreningar grafit fluorider och nanoporösa O2-eroderade grafit. Magnetiska egenskaperna hos dessa system är starkt beroende av strukturen, och kan fint avstämmas genom att man ändrar π-elektronsystem av grafit, i. e. med graden av fluorering av inskjutna föreningar och genom införandet av bor föroreningar till värd matris av nanoporösa grafit.

Place, publisher, year, edition, pages
Umeå University, 2012. 77 p.
Keyword
carbon nanotube, fullerene, single molecular magnet, Mn12, graphite fluoride, nanoporous carbon, molecular magnetism, magnetic properties, SQUID magnetometry, x-ray diffraction, Raman spectroscopy
National Category
Physical Sciences
Research subject
Materials Science
Identifiers
urn:nbn:se:umu:diva-53568 (URN)987-91-7459-396-9 (ISBN)
Public defence
2012-04-27, Naturvetarhuset, N200, Umeå Universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2012-04-04 Created: 2012-04-02 Last updated: 2012-05-23Bibliographically approved

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