Effect of spin substitution on stripe order in ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{Cu}}_{1-y}{\mathrm{M}}_y{\mathrm{O}}_4$ $(M=\mathrm{Zn}$ or $\mathrm{Ni})$

The destruction of stripe order by Zn $\mathrm{}(S=0\mathrm{})\mathrm{}$ and the formation of a new phase by Ni $\mathrm{}(S=1\mathrm{})\mathrm{}$ are demonstrated directly from the substitution dependence of the electronic coefficient of specific heat $\gamma$ in ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{Cu}}_{1-y}{M}_y{\mathrm{O}}_4$ $(M=\mathrm{Zn}$ or Ni). In the Zn-substitution case, γ, which is strongly suppressed by stripe phase formation, increases to a value that corresponds to the state where there is no stripe order. In the Ni-substitution case, γ saturates at nearly half the value of the Zn-substitution case. The difference can be explained by a difference in the spin interactions between the substituent atom and the nearest neighbor Cu atoms, indicating that spin interaction plays an important role in the formation of charge stripes.