Microwave response to a magnetic phase transition in a molecular magnet based on [Mn12O12( Me CO2)16(H2O)4] clusters and tetramethyltetrathiafulvalene molecules

The electron paramagnetic resonance spectra of a molecular magnet synthesized from [Mn₁₂O₁₂(MeCO₂)₁₆(H₂O)₄] high-spin clusters and tetramethyltetrathiafulvalene donor organic molecules are investigated. It is revealed that, in the temperature range 5–7 K, there appears an additional signal against the background of the ferromagnetic resonance spectrum. The additional signal consists of a large number of lines and has a resonance nature, because it is observed in the well-reproduced narrow ranges of the constant magnetic field of the spectrometer (300–650 and 850–1300 Oe) at a frequency of 9.4152 GHz. The appearance of the additional signal at a temperature of 5 K is attended by a multiple increase in the magnetic susceptibility of the sample. There is a correlation between the spectral characteristics of the additional signal (such as the average amplitude, the spectral power, etc.) and the parameters of the ferromagnetic resonance spectrum (the resonance field, the linewidth, and the integrated intensity). The assumption is made that the additional signal is associated with the magnetic-field-induced transitions between spin states of Mn₁₂ high-spin clusters for different orientations of crystallites with respect to the external magnetic field. Original Russian Text ? R.B. Morgunov, V.L. Berdinskiĭ, A.I. Dmitriev, Y. Tanimoto, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 5, pp. 945–950.