Anion substitution effects on the structure and magnetism of the chromium chalcogenide Cr{sub 5}Te{sub 8}-Part III: Structures and magnetism of the high-temperature modification Cr{sub (1+x)}Q{sub 2} and the low-temperature modification Cr{sub (5+x)}Q{sub 8} (Q=Te, Se; Te:Se=5:3)
- Institute of Inorganic Chemistry, Christian-Albrechts-University Kiel, Olshausenstr. 40, D-24098 Kiel (Germany)
- Department of Chemistry, LMU Munich, Butenandstr. 3-13, D-81377 Munich (Germany)
- Max-Planck Institut fuer Festkoerperforschung, Heisenbergstr. 1, D-70506 Stuttgart (Germany)
The title compounds were synthesized via the high-temperature (HT) route. The materials are characterized by Rietveld analysis, magnetic measurements, and electronic band-structure calculations. Two different structural modifications depending on the synthesis conditions are observed: a HT modification with trigonal basic cells (space group: P-3m1) for Cr{sub (1+x)}Q{sub 2} ((1+x)=1.25, 1.28, 1.34, 1.37, 1.41, 1.43) and a low-temperature (LT) modification with trigonal super-cell (space group: P-3m1) for Cr{sub (5+x)}Q{sub 8} ((5+x)=5.00, 5.12, 5.36, 5.48, 5.64, 5.72). The crystal structures are closely related to the NiAs-type structure with metal vacancies in every second metal layer. The substitution of Te by Se and the change of the Cr concentration induce significant alterations of the magnetic properties. With increasing Cr content the Weiss constant {theta} changes drastically from negative to strong positive values, i.e., with increasing Cr concentration a shift from predominant antiferromagnetic exchange to ferromagnetic exchange occurs. At LTs a complex magnetic behavior is observed. For some members a spin-glass (SG) behavior is found with the freezing temperature T{sub f} following the Vogel-Fulcher law. At the highest Cr concentrations ferromagnetic characteristics dominate with spontaneous magnetizations below the Curie temperatures. The differences of the magnetic properties of the LT and HT phases can be explained on the basis of interatomic distances and angles. For a deeper understanding of the experimental results, they have been compared with the results of spin polarized relativistic Korringa-Kohn-Rostoker electronic band-structure calculations and both results are consistent. To explain the features of temperature-dependent magnetization of the compounds, Monte Carlo (MC) simulations based on the Heisenberg model have been performed with the exchange coupling parameters obtained within the ab-initio calculations of the electronic structure. The possible reasons for a modification of the exchange coupling parameters responsible for the temperature-dependent features are also analyzed. - Graphical abstract: The magnetic properties of Cr{sub 1+x}Q{sub 2} and Cr{sub 5+x}Te{sub 5}Se{sub 3} (Q=Te, Se; ratio=5:3) are strongly influenced by the Cr content and the crystal structure with the Weiss constant and Curie temperature covering a large range.
- OSTI ID:
- 21128337
- Journal Information:
- Journal of Solid State Chemistry, Vol. 181, Issue 6; Other Information: DOI: 10.1016/j.jssc.2008.03.021; PII: S0022-4596(08)00153-9; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
Similar Records
Crystal structures, unusual magnetic properties and electronic band structures of Cr{sub 5-x}Ti{sub x}Te{sub 8}
Ferromagnetism in diluted Pb{sub 1-x-y}Ge{sub x}Cr{sub y}Te magnetic semiconductors
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ANTIFERROMAGNETISM
CHROMIUM SELENIDES
CHROMIUM TELLURIDES
CURIE POINT
ELECTRONIC STRUCTURE
HEISENBERG MODEL
INTERATOMIC DISTANCES
MAGNETIC PROPERTIES
MAGNETIZATION
MONTE CARLO METHOD
RELATIVISTIC RANGE
SPACE GROUPS
SPIN GLASS STATE
SPIN ORIENTATION
SYNTHESIS
TRIGONAL LATTICES
VACANCIES