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Published on: March 24, 2019
A 236-GHz Fe EPR STUDY OF NANO-PARTICLES OF THE FERRO-MAGNETIC ROOM-TEMPERATURE SEMICONDUCTOR
Sushil K Misra1, S I Andronenko, A Punnoose
1Physics Department, Concordia University, 1455 de Maisonneuve Boulevard West. Montreal, QC H3G 1M8, Canada.
Abstract:
High frequency (236 GHz) electron paramagnetic resonance (EPR) studies of Fe(3+) ions at 255 K are reported in a Sn(1-x)Fe(x)O(2) powder with x = 0.005 which is a ferromagnetic semiconductor at room temperature. The observed EPR spectrum can be simulated reasonably well as overlap of spectra due to four magnetically inequivalent high-spin (HS) Fe(3+) ions (S = 5/2). The spectrum intensity is calculated, using the overlap I(BL) + (I(HS1)+I(HS2)+I(HS3)+I(HS4))×e(-0.00001×B), where B is the magnetic field intensity in Gauss, I represents the intensity of an EPR line (HS1, HS2, HS3, HS4), and BL stands for the base line. (The exponential factor, as found by fitting to the experimental spectrum, is related to the Boltzmann population distribution of energy levels at 255 K, which is the temperature of the sample in the spectrometer.) These high-frequency EPR results are significantly different from those at X-band. The large values of the zero-field splitting parameter (D) observed here for the four centers at the high frequency of 236 GHz are beyond the capability of X-band, which can only record spectra of ions only with much smaller D values than those reported here.
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When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
