Neutron Scattering Study of Magnetic Field Effect on the Stripe Order in LBCO

We have been investigating the relationship of stripe order to high-temperature superconductivity in cuprates. In particular, our neutron scattering results indicate that spin-stripe order is present in La$_{2-x}$Ba$_{x}$CuO$_{4}$ (LBCO) over a substantial range of doping about x = 1/8, where the bulk superconductivity is anomalously suppressed. Focusing on the x = 1/8 composition, we have recently studied the impact on stripe order of a magnetic field applied along the c-axis [1]. Applying a field up to 7 T, we observed a small enhancement of the intensity of the incommensurate antiferromagnetic superlattice peaks and a slight increase in the ordering temperature. In measurements of the spin dynamics, the field had no significant impact on the small spin gap ($\sim $ 0.5 meV) found in the ordered phase [2]. [1] Jinsheng Wen \textit{et al}., arXiv:0810.4085. [2] J.M. Tranquada \textit{et al}., arXiv:0809.0711. Work supported by Office of Science, U.S. DOE, under Contract No. DEAC02-98CH10886