A 236 GHz Fe 3 + EPR Study of Nanoparticles of the Ferromagnetic Room - Temperature Semiconductor Sn 1 2 x Fe x O 2 ( x 5 0 . 005 )

High-frequency (236 GHz) electron paramagnetic resonance (EPR) studies of Fe ions at 255 K are reported in a Sn1-xFexO2 powder with x = 0.005, which is a ferromagnetic semiconductor at room temperature. The observed EPR spectrum can be simulated reasonably well as the overlap of spectra due to four magnetically inequivalent high-spin (HS) Fe ions (S = 5/2). The spectrum intensity is calculated, using the overlap I(BL) ? (I(HS1) ? I(HS2) ? I(HS3) ? I(HS4)) 9 exp(-0.00001B), 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 baseline (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 with much smaller D values than those reported here. S. K. Misra (&) S. I. Andronenko Physics Department, Concordia University, 1455 de Maisonneuve Boulevard West, Montreal, QC H3G 1M8, Canada e-mail: [email protected] A. Punnoose Department of Physics, Boise State University, Boise, ID 83725-1570, USA D. Tipikin J. H. Freed ACERT Biomedical Center, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA 123 Appl Magn Reson (2009) 36:291–295 DOI 10.1007/s00723-009-0024-4 Applied