Ho-doping effect on the incommensurate magnetic order in La_1.88Sr_0.12CuO₄

We have performed elastic neutron scattering experiments on the superconductor La_1.85Ho_0.03Sr_0.12CuO₄ to study the effect of substitution of a cation with a large magnetic moment at La site on the static spin correlation. In the Ho-free sample with a hole concentration of 0.12, the spatially-modulated magnetic order is known to be stabilized at temperature below T _spin ∼30 K. In the present Ho-doped sample, we found the appearance of magnetic peaks at (0.5, 0.5 ± 0.119, 0) positions below T _spin ∼35 K, which is similar to the observation in the pristine sample. Furthermore, the volume-corrected intensities in the Ho-free and Ho-doped samples are comparable, suggesting a negligible effect of Ho-substitution at La sites. These results are quite a contrast to the huge enhancement of the magnetic intensity and the increase of T _spin by substituting a comparable amounts of magnetic Fe³⁺ ions onto CuO₂ planes. Therefore, the stability of the stripe order induced by the cation substitution is sensitive to the site at which the substitution occurs.