Charge stripe glasses in La2-xSrxNiO4 for 0.20 < x < 0.25

We present high resolution X-ray measurementscharacterising the charge stripe order state in theLa_2-xSr_xNiO₄ system with x = 0.20, 0.225 and 0.25. Wefind that in the x = 0.20, 0.225 and 0.25 systems the chargestripe order exists in a charge stripe glass characterised byweak, poorly correlated incommensurate charge stripes in contrastto the strong well correlated charge stripes in the commensuratex = 1/3 system. No stabilisation of the charge order wasobserved at the next possible commensurate value of ε= 0.25. A comparison with high energy X-ray measurements suggestedthat the charge order may exist in a charge stripe glass in thebulk in the doping region x = 0.20 - 0.33. Finally at lowtemperature there was an initial increase in the intensity andcorrelation not observed with neutron measurements and it appearsto be an effect that X-rays are sensitive to but neutrons are not.