MAGNETIC RESONANCES AND MAGNETIZATION IN THE SPIN LADDER COMPOUND (VO)(2)P2O7

We present experimental results of magnetic susceptibility, magnetizat ion and magnetic resonances on the S=1/2 spin ladder system vanadyl py rophospate [(VO)(2)P2O7] In this system a spinware excitation gap of t he order of E(G)=50 K was observed with inelastic neutron scattering e xperiments at the boundary of the Brillouin zone. Our measurements wer e performed in powder samples in magnetic fields up to 14 T at tempera tures down to 1.5 K and in the frequency range 55-345 GHz. We found a linear resonance branch corresponding to a g-factor g=1.98. Strong evi dence for chain end effects was observed in susceptibility and magneti zation data as well as in the temperature dependence of the absorption line intensity. The lineshape of the observed resonances points to a slightly anisotropic g-tensor. In higher fields we resolve the single resonance branch into several distinguished absorption lines with diff erent temperature dependences. Copyright (C) 1996 Elsevier Science Ltd