ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Magnetic properties of the synthetic hexafluoroantimonate complex of iron (III) tetraphenylporphyrin, Fe(TPP) (FSbF5)⋅C6H5F, were studied by susceptibility and Mössbauer techniques. The measured effective magnetic moment varies from 1.7 β at 1.5 K to 4.14 β at 300 K. The data were analyzed with the "Maltempo model'' combined with a mean field antiferromagnetic treatment. This analysis shows that the system is predominantly in the S=3/2 spin state (98%) with an unusually small spin–orbit coupling constant ζ=79 cm−1. The net interaction of a given spin with the thermal average of all the spins is (1.39 cm−1)S⋅〈S〉T. Mössbauer spectra were recorded from 4.2 to 64 K in fields 0 to 6 T. The chemical shift δ=0.39 (Fe) mm/s and quadrupole splitting ΔE=4.29 mm/s are temperature independent and typical of ferric ions in the admixed–intermediate spin state. Mössbauer analysis confirms that the exchange interaction must couple many spins rather than forming spin pairs as seen in earlier work. The analysis also provides the rather low hyperfine coupling constant P/gNβN=28 T/unit spin, and contact constant κ=0.25. The spectra imply slow relaxation in fields greater than 4 T at 4.2 K, the rate increasing with increasing T and decreasing H. All Mössbauer and susceptibility data were fitted with a common parameter set; only the relaxation parameter was varied from one spectrum to another.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.452552
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