Electron spin resonance shift in spin ladder compounds
  We analyze the effects of different coupling anisotropies in spin-1/2 ladder on the Electron Spin Resonance (ESR) shift. Combining a perturbative expression in the anisotropies with temperature dependent Density Matrix Renormalization Group (T-DMRG) computation of the short range correlations, we provide the full temperature and magnetic field evolution of the ESR paramagnetic shift. We show that for well chosen parameters the ESR shift can be in principle used to extract quantitatively the anisotropies and, as an example, discuss the material $\mathrm{(C_5H_{12}N)_2CuBr_4}$ (BPCB). 
Shunsuke C. Furuya, Pierre Bouillot, Corinna Kollath, Masaki Oshikawa,   Thierry Giamarchi
cond-mat.str-el