Magnetic studies reveal near-perfect paramagnetism in the molecular semiconductor vanadyl phthalocyanine (C32H16N8VO)

Temperature (0.5–300K) and magnetic field (H up to 90kOe) dependences of the magnetization (M) of a powder sample of vanadyl phthalocyanine (VOPc) having the Phase II-triclinic structure are measured and analyzed. The data of χ = M/H vs. T measured in H = 1kOe fit the modified Curie-Weiss (CW) law,...

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Bibliographic Details
Published in:Journal of magnetism and magnetic materials 2017-01, Vol.422, p.386-390
Main Authors: Wang (王正君), Zhengjun, Pi, Li, Seehra, Mohindar S., Bindra, Jasleen, van Tol, Hans, Dalal, Naresh S.
Format: Article
Language:English
Subjects:
Antiferromagnetism
Coupling (molecular)
Electron paramagnetic resonance
Magnetic fields
Magnetic molecular semiconductors
Magnetic moments
Magnetic resonance
Magnetic susceptibility
Magnetism
Paramagnetism
Saturation magnetization
Semiconductors
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Summary:Temperature (0.5–300K) and magnetic field (H up to 90kOe) dependences of the magnetization (M) of a powder sample of vanadyl phthalocyanine (VOPc) having the Phase II-triclinic structure are measured and analyzed. The data of χ = M/H vs. T measured in H = 1kOe fit the modified Curie-Weiss (CW) law, χ = χo+C/(T−θ), with C = 6.266×10−4 emuK/gOe, θ = −0.1K and χo = −9.3×10−7emu/gOe. The Curie constant C yields magnetic moment μ = 1.704μB, S = 1/2, and g = 1.967 characteristic of VO2+. The magnitude of θ = −0.1K signifying very weak inter-ion antiferromagnetic exchange coupling is supported by the analysis of the variable frequency (9.8–336GHz) electron paramagnetic resonance data. The isothermal data of M vs. H at ten temperatures between 0.5K and 300K when plotted as M vs. H/(T+0.1) collapses on to a single curve given by M = Motanh {gμBH/[2kB(T+0.1)]} with Mo = NgμBS = 9.48emu/g expected for S = 1/2 system, thus signifying near perfect paramagnetism in VOPc. [Display omitted] •Magnetization M vs. temperature T from 0.5K to 300K in H = 1kOe is reported.•M vs. T data fit Curie-Weiss law with θ = −0.1K, S = 1/2, &g = 1.967 for VO2+.•Isothermal M vs. H data (H up to 90kOe) for ten T from 0.5K to 300K is reported.•M vs. H/(T−θ) plot for various T fit a single Brillouin function curve for S = 1/2.•Analysis of magnetic and EPR data in VOPc shows near perfect S = 1/2 paramagnetism.
ISSN:0304-8853
1873-4766
DOI:10.1016/j.jmmm.2016.09.018