CHARGE-ORDERED STATES IN (LA,SR)2NIO4 FOR HOLE CONCENTRATIONS N(H)=1/3 AND N(H)=1/2

Real-space ordering of doped holes in La2-xSrxNiO4 is revealed in magnetic and electronic-transport anomalies at low temperatures. The ordering is most pronounced for a hole concentration n(h) of 1/3 below 235 K where a superlattice with a modulation wave vector 8 of 1/3 has been found. For n(h) = 1/2, another charge-ordered state with delta = 0 is also indicated below approximately 340 K. Our results are, furthermore, suggestive of mesoscopic hole segregation for 0.2 less-than-or-equal-to x less-than-or-equal-to 0.4 forming the n(h) = 1/3 and delta = 1/3 state below 235 K.