Anomalous Magnetic Properties of Ti5O9

Abstract

A magnetic susceptibility study from 77° to almost 900°K and an electron-spin-resonance study from 77° to 160°K of Ti5O9 shows an anomalous magnetic behavior. The magnetic susceptibility gives a peak in its temperature dependence which resembles a Néel temperature and can be interpreted to indicate antiferromagnetic-like behavior. The magnetic susceptibility peak occurs at about 130°K. An x-ray study of Ti5O9 indicates face sharing anion octahedra with a short metal-metal distance which lends support to a cation-cation interaction model. The electron-spin-resonance (ESR) study gives spectra which yield g values of 1.98±0.02. This indicates little orbital contribution to the magnetic moment. The spectral linewidth increases sharply with increasing temperature in the region of the magnetic susceptibility maximum, showing effects of electron-phonon interactions. The signal intensity decreases rapidly above this susceptibility peak. The line shape is asymmetric below this temperature region, however, it becomes symmetrical above it. The behavior presented in these results reflects a complex effect undoubtedly involving delocalized electrons in which a low-temperature electron localization may occur. The value of the magnetic moment of Ti3+ in Ti5O9 is, therefore, not clear. While some of these results indicate an apparent antiferromagnetic behavior and appear to support the cation-cation interaction model, they cannot be completely resolved as such. The crystalline distortion present may contribute to the trapping of the electrons at low temperatures, and thus facilitate the cation-cation interactions and influence the spin-lattice relaxation times.