Photoacoustic spectra of low-dimensional magnet of VOMoO4

Crystal of VOMoO4 is constituted from linear chains of VO6 octahedra along the c-axis. Every chain is connected with each other through MoO4 tetrahedr a. The temperature dependent behavior of magnetic susceptibility shows a br oad maximum around 100 K. That suggests a characteristic of one-dimensional antiferromagnet. Although optical absorption measurements are important to investigate electronic structure of materials at first step, few investiga tions on its characteristics have been carried out. In this paper, we repor t on the optical absorption properties of VOMoO4 by photoacoustic (PA) spec troscopy. It is useful to obtain absorption characteristics for strongly sc attering media such as small sized crystals of VOMoO4 because its signal is less sensitive to light scattering effects. Although there were no dearly predominant interband transition, the optical absorption edge of VOMoO4 is assumed to be direct allowed transition because the square of the PA signal intensities are proportional to photon energy. Thus, the direct allowed ba nd-gap energy for VOMoO4 is obtained as 1.6 eV for the first time by PA spe ctroscopic technique.