Structural, magnetic, and electronic properties of iron selenide Fe{sub 6-7}Se{sub 8} nanoparticles obtained by thermal decomposition in high-temperature organic solvents

Journal Article · Mon Jul 28 00:00:00 EDT 2014 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4887356· OSTI ID:22419954

Funtov, K. O.; Dmitrieva, T. V.; Starchikov, S. S. ^[1]; Lin, Chun-Rong ^[2]; Siao, Yu-Jhan ^[3]; Chen, Mei-Li ^[4]

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1. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow 119333 (Russian Federation)
2. Department of Applied Physics, National Pingtung University of Education, Pingtung 90003, Taiwan (China)
3. Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, Tainan 71005, Taiwan (China)
4. Department of Electro-optical Engineering, Southern Taiwan University of Science and Technology, Tainan 71005, Taiwan (China)

Iron selenide nanoparticles with the NiAs-like crystal structure were synthesized by thermal decomposition of iron chloride and selenium powder in a high-temperature organic solvent. Depending on the time of the compound processing at 340 °C, the nanocrystals with monoclinic (M)-Fe{sub 3}Se{sub 4} or hexagonal (H)-Fe{sub 7}Se{sub 8} structures as well as a mixture of these two phases can be obtained. The magnetic behavior of the monoclinic and hexagonal phases is very different. The applied-field and temperature dependences of magnetization reveal a complicated transformation between ferrimagnetic (FRM) and antiferromagnetic (AFM) structures, which can be related to the spin rotation process connected with the redistribution of cation vacancies. From XRD and Mössbauer data, the 3c type superstructure of vacancy ordering was found in the hexagonal Fe{sub 7}Se{sub 8}. Redistribution of vacancies in Fe{sub 7}Se{sub 8} from random to ordered leads to the transformation of the magnetic structure from FRM to AFM. The Mössbauer data indicate that vacancies in the monoclinic Fe{sub 3}Se{sub 4} prefer to appear near the Fe{sup 3+} ions and stimulate the magnetic transition with the rotation of the Fe{sup 3+} magnetic moments. Unusually high coercive force H{sub c} was found in both (H) and (M) nanocrystals with the highest (“giant”) value of about 25 kOe in monoclinic Fe{sub 3}Se{sub 4}. This is explained by the strong surface magnetic anisotropy which is essentially larger than the core anisotropy. Such a large coercivity is rare for materials without rare earth or noble metal elements, and the Fe{sub 3}Se{sub 4}-based compounds can be the low-cost, nontoxic alternative materials for advanced magnets. In addition, an unusual effect of “switching” of magnetization in a field of 10 kOe was found in the Fe{sub 3}Se{sub 4} nanoparticles below 280 K, which can be important for applications.

• OSTI ID: 22419954
• Journal Information: Journal of Chemical Physics, Vol. 141, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
77 NANOSCIENCE AND NANOTECHNOLOGY
ANISOTROPY
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ATOMIC FORCE MICROSCOPY
COERCIVE FORCE
IRON
IRON CHLORIDES
IRON IONS
MAGNETIZATION
MAGNETS
MONOCLINIC LATTICES
NANOPARTICLES
NANOSTRUCTURES
ORGANIC SOLVENTS
PYROLYSIS
X-RAY DIFFRACTION