Field-induced magnetic order in La_2-xSr_xCuO ₄ (x=0.10,0.115,0.13) studied by in-plane thermal conductivity measurements

We have measured the thermal conductivity in the ab plane of La _2-xSr_xCuO₄ (x=0, 0.10,0.115,0.13) in magnetic fields up to 14 T parallel to the c axis and also parallel to the ab plane. By the application of magnetic fields parallel to the c axis, the thermal conductivity has been found to be suppressed at low temperatures below the temperature T_K which is located above the superconducting transition temperature and is almost independent of the magnitude of the magnetic field. The suppression is marked in x=0.10 and 0.13, while it is small in x=0.115. Furthermore, no suppression is observed in the 1% Zn-substituted La _2-xSr_xCu_0.99Zn_0.01O₄ with x=0.115. Taking into account the experimental results that the temperature dependence of the relative reduction of the thermal conductivity is quite similar to the temperature dependence of the intensity of the incommensurate magnetic Bragg peak corresponding to the static stripe order and that the Zn substitution tends to stabilize the static order, it is concluded that the suppression of the thermal conductivity in magnetic fields is attributed to the development of the static stripe order. The present results suggest that the field-induced magnetic order in La_2-xSr_xCuO₄ originates from the pinning of the dynamical stripes of spins and holes by vortex cores.