Inhomogeneous magnetic cluster states in the magnetoresistance material Lu2V2O7

We report Raman scattering and multifrequency (54–336 GHz) electron-spin-resonance (ESR) measurements on Lu2V2O7 single crystals in the temperature range 4–300 K with the view of understanding the origin of the large magnetoresistance in this lattice. The 307 cm−1 phonon mode undergoes a hardening at temperatures below Tm=150 K. Concomitantly, the single ESR peak arising from the paramagnetic V4+ ions becomes distorted. This is ascribed to the development of short-range magnetic correlations leading to a formation of magnetic clusters. Below the Curie temperature TC=70 K the ESR line develops with fine structures, indicative of an inhomogeneous ground state. Between Tm and TC the magnetic cluster concentration decreases strongly as a function of the applied magnetic field, suggesting that the large magnetoresistance of this material could be due to the magnetic inhomogeneity in this lattice. The origin of what causes the initiation of such clusters is still unclear.