TY - JOUR
T1 - Paramagnetic resonance and non-resonant microwave absorption in iron niobate
AU - Alvarez, G.
AU - Font, R.
AU - Portelles, J.
AU - Raymond, O.
AU - Zamorano, R.
N1 - Funding Information:
G. Alvarez acknowledges a postdoctoral fellowship from UNAM-Mexico.
PY - 2009/4
Y1 - 2009/4
N2 - An electron paramagnetic resonance (EPR) study of FeNbO4 powder samples in monoclinic phase (wolframite-type) at X-band (8.8-9.8 GHz), in the 90-300 K temperature range, is presented. For all the temperatures, the EPR spectrum shows a single line associated with Fe3+ ions. Changes in the lineshape of the EPR spectrum, which can be attributed to Fe2+ ions, are detected at low temperatures. This behavior can be ascribed to a strong magnetic dipolar interaction between Fe2+ and Fe3+ ions. The non-resonant microwave absorption techniques: magnetically-modulated microwave absorption spectroscopy (MAMMAS) and low-field microwave absorption spectroscopy (LFMAS), were used for a further knowledge on this material. MAMMAS response suggests also the presence of Fe2+ ions, that originates a change in microwave absorption regime for T < Tp (=140 K), associated with the presence of short-range magnetic correlations. LFMAS spectra showed a linear behavior with positive slope and non-hysteretic traces. The profiles obtained by plotting the slope vs. temperature of the LFMAS line are similar to those detected by the MAMMAS technique, confirming that both types of measurement show the same processes of absorption.
AB - An electron paramagnetic resonance (EPR) study of FeNbO4 powder samples in monoclinic phase (wolframite-type) at X-band (8.8-9.8 GHz), in the 90-300 K temperature range, is presented. For all the temperatures, the EPR spectrum shows a single line associated with Fe3+ ions. Changes in the lineshape of the EPR spectrum, which can be attributed to Fe2+ ions, are detected at low temperatures. This behavior can be ascribed to a strong magnetic dipolar interaction between Fe2+ and Fe3+ ions. The non-resonant microwave absorption techniques: magnetically-modulated microwave absorption spectroscopy (MAMMAS) and low-field microwave absorption spectroscopy (LFMAS), were used for a further knowledge on this material. MAMMAS response suggests also the presence of Fe2+ ions, that originates a change in microwave absorption regime for T < Tp (=140 K), associated with the presence of short-range magnetic correlations. LFMAS spectra showed a linear behavior with positive slope and non-hysteretic traces. The profiles obtained by plotting the slope vs. temperature of the LFMAS line are similar to those detected by the MAMMAS technique, confirming that both types of measurement show the same processes of absorption.
KW - Electron paramagnetic resonance (EPR)
KW - Mixed valency oxides
KW - Non-resonant microwave absorption
UR - http://www.scopus.com/inward/record.url?scp=63449092153&partnerID=8YFLogxK
U2 - 10.1016/j.solidstatesciences.2008.11.001
DO - 10.1016/j.solidstatesciences.2008.11.001
M3 - Artículo
SN - 1293-2558
VL - 11
SP - 881
EP - 884
JO - Solid State Sciences
JF - Solid State Sciences
IS - 4
ER -