Effect of annealing on magnetic
resonance spectra of Ti-Si-C-N
sample
1,2 3 2 2
N. Guskos , E. A. Anagnostakis , G. Zolnierkiewicz , J. Typek ,
4 2
A. Biedunkiewicz , and A. Guskos
1
Solid State Section, Department of Physics, University of Athens, Panepistimiopolis, 15 784 Zografos, Athens, Greece
2
Institute of Physics, West Pomeranian University of Technology, Al. Piastow 48, 70-311 Szczecin, Poland
3
Department of Computer and Communication Engineering, University of Thessaly, Deligiorgi Building, 382 21 Volos, Greece
4
Institute of Materials Science and Engineering, West Pomeranian University of Technology, Al. Piastow 19, 70-310 Szczecin, Poland
Abstract
Two nanocrystalline (TiC + SiC)/C samples have been prepared by non-x hydrolytic sol-gel method. The second sample was subjected to additional
annealing in NH atmosphere at 1623 K. The XRD measurements showed the 3
presence of aggregates of cubic SiC+TiC nanoparticles (10 to 30 nm in size). In both samples a very narrow electron paramagnetic resonance (EPR) line arising from magnetic localized centers was centered at g ~2 (the differences in the eff resonance fields of both samples were 0.6 Gs). At T=130 K the linewidths ÄH =1.41(2) Gs and ÄH =2.92(2) Gs were registered for samples without and pp pp with thermal annealing, respectively. For the non-annealed sample the resonance line could be fitted by Lorentzian line in the high temperature range and by Dysonian line below 70 K. This indicates on an essential change of the electrical conductivity of this sample. For annealed sample the resonance lineshape was Dysonian in the whole investigated temperature range. Thus, the thermal annealing process could improve significantly the transport properties. An analysis of temperature dependence of the EPR parameters (g-factor, linewidth, integrated intensity) has shown that the thermal annealing process essential influenced the reorientation process of the localized magnetic centers.
3360 3380 3400 -15000 -10000 -5000 0 5000 10000 15000 d c "/ d H [A rb . u n it s ] Magnetic field H [Gs] 130 K 3.7 K 3370 3372 3374 3376 3378 3380 -12000 -10000 -8000 -6000 -4000 -2000 0 2000 4000 6000 d c "/ d H [A rb . u n it s ] Magnetic field H [Gs] 90 K 290 K DT=10 K 3360 3380 3400 -80000 -60000 -40000 -20000 0 20000 40000 60000 80000 d c "/ d H [A rb . u n it s ] Magnetic field H [Gs] 3.8 K 130 K 3370 3372 3374 3376 3378 3380 -20000 -15000 -10000 -5000 0 5000 10000 15000 d c "/ d H [A rb . u n it s ] Magnetic field H [Gs] 290 K 90 K 50 100 150 200 250 3373 3374 3375 3376 3377 3378 3379 3380 Sample 1 Sample 2 R e s o n a n c e fi e ld H r [G s ] Temperature T [K] 50 100 150 200 250 2 4 6 8 10 Sample 1 Sample 2 L in e w id th D H p p [G s ] Temperature T [K] 50 100 150 200 250 0 2000000 4000000 6000000 8000000 Sample 1 Sample 2 In te g ra te d in te n s it y I inte g r [A rb . u n it s ] Temperature T [K] 50 100 150 200 250 0.00000 0.00005 0.00010 0.00015 0.00020 Sample 1 Sample 2 1 /I in te g r Temperature T [K]
Figure 1. EPR spectra of Ti-Si-C-N sample at different temperatures: before annealing (a) and after high-temperature annealing (b). The left panels show the spectra in the low-temperature range, the right panels in the high-temperature range.
Figure 2. Temperature dependence of the EPR parameters of Ti-Si-C-N sample (resonance field, linewidth, integrated intensity, reciprocal of integrated intensity): before annealing (sample 1) and
after high-temperature annealing (sample 2).
a) a)
