Is stripe incommensurability in La_{2-x}Sr_xCoO_4 proportional to doping?

Abstract: The longstanding notion of stripe incommensurability being proportional to doping, \delta(x) ~ x, in lanthanum transition-metal oxides, La_{2-x}Sr_xTmO_4 (Tm = Cu, Ni, Co), is partly borne out by experiment but also plagued with exceptions. Future neutron-scattering experiments on cobaltates could provide a clear distinction whether a linear or square-root dependence, \delta(x) ~ sqrt(x - x_0), is valid.