Magnetic resonance study of
Sb V Mo O
3
2
3
21
1 1 1 2
J. Typek , N. Guskos ,G. Zolnierkiewicz and E. Filipek
1Institute of Physics, West Pomeranian University of Technology, 70-311 Szczecin, Al. Piastow 48, Poland
2
Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, 71-065 Szczecin,
Al. Piastow 42, Poland
3100 3200 3300 3400 3500 3600 3700 3800 3900 -30 -20 -10 0 10 20 30 E P R s ig n a l a m p lit u d e [a rb . u n it s ] Magnetic field [Gs] 4K 8K 16.4K 30.5K 45K 60K 75K 90K 120K 150K 180K 210K 240K 270K 290K 4 K 290 K 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 1.935 1.940 1.945 1.950 1.955 1.960 1.965 1.970 1.975 gx gy gz g -f a c to r Temperature [K] 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 0 100 200 300 400 500 600 700 wx wy wz L in e w id th s [M H z] Tem perature [K] 4 6 8 10 12 14 1.945 1.950 1.955 1.960 1.965 1.970 1.9750 100 200 300 400 500 600 gx gy gz g -f a c to r Temperature [K] wx wy wz L in e w id th [M H z ] 0 10 20 30 40 50 60 70 0 50 100 150 200 250 300 200 400 600 800 1000 1200 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 I EP R [a rb . u n it s ] I=671.14/(T+9.8) for T(10-150K) I EP R *T [a rb . u n it s ] Temperature [K] 1 /I E P R
Abstract
The Sb V Mo O compound is formed in the three-component oxide system á-Sb O -V O -MoO from an appropriate amount of 3 2 3 21 2 4 2 5 3 these oxides by using the solid-state reaction method. It crystallizes in rhombic system (Z=4) with the following values of unit cell parameters: a=2.0241 nm, b=0.8449 nm, c=0.8169 nm at room temperature. Electron paramagnetic resonance (EPR) study of Sb V Mo O has been carried out in the 4-290 K temperature range. Comparison with VOSO ?5H O intensity standard revealed that 3 2 3 21 4 2 only 11.3% of all vanadium ions in Sb V Mo O are paramagnetic V(IV) species. The temperature dependence of the calculated EPR 3 2 3 21 parameters (g-factor, linewidth, integrated intensity) has been studied and the obtained results are correlated with the proposed magnetic properties of V(IV) single ions and clusters.
Conclusions
5+ 4+
· Most of vanadium in Sb V Mo O appears as nonmagnetic V species (88.7%), only 11.3% as paramagnetic V ions and clusters.3 2 3 21
4+
· No isolated non-interacting V ions are visible in the EPR spectrum of Sb V Mo O . Most observable paramagnetic centers 3 2 3 21
4+
involve strongly interacting V ions and vanadium clusters.
· Strong changes of magnetic anisotropy of the spin system with temperature are registered. The z-component of g-factor displays a peculiar thermal dependence reflecting the symmetry changes o the complex.
· As the magnetic interactions in the spin system of Sb V Mo O compound are concerned three different temperature ranges could 3 2 3 21 be recognized: the low-temperature range (>10 K), the intermediate temperature range (10-150 K) and the high-temperature range (<270 K). In the low-temperature range an approach to an ordered magnetic state is visible in large shifts of the resonance fields and an abrupt increase of anisotropic linewidths. In the intermediate temperature range an antiferromagnetic interaction between paramagnetic centers is deduced from the temperature dependence of EPR integrated intensity. In the high-temperature range an additional magnetic contribution is registered, probably from antiferromagnically coupled vanadium pairs.
Figure 5. Temperature dependence of the EPR integrated intensity (top panel), reciprocal of integrated intensity (middle panel) and the product of temperature and integrated intensity (bottom panel).
Figure 4. Temperature dependence of the anisotropic linewidths (top panel) and g-factors (bottom panel) in the 4-14 K temperature range. Figure 3. Temperature dependence of the anisotropic linewidths of
Sb V Mo O in the 4-290 K range.3 2 3 21
Figure 1. Selection of EPR spectra of Sb V Mo O powder samples 3 2 3 21 registered at different temperatures in the 4-290 K range.
Figure 2. Temperature dependence of the anisotropic g-factors of Sb V Mo O in the 4-290 K range.3 2 3 21
