Charge and spin ordering inLa2−xSr

Microscopic origin of diagonal stripe phases in doped nickelates

“…They have been observed in a variety of systems, including nickelates, 1,2,3,4,5,6,7,8 cuprates, 9,10,11,12,13,14,15 and manganites. 16,17,18 Among them, layered La 2−x Sr x CuO 4 (LSCO), La 2−x−y Nd y Sr x CuO 4 (Nd-LSCO), La 2−x Sr x NiO 4 (LSNO), and La 2 NiO 4+δ (LNO) compounds play plausibly the most prominent role.…”

“…More precisely, neutron scattering measurements have revealed static stripe order in the LNO samples with δ = 0.105, 0.125, as well as 0.133, 25,26,27,28,29,30,31 and even over a wider hole doping regime 0.135 ≤ x ≤ 0.5 in the case of LSNO. 1,2,3,4,5,6,7,8 Moreover, the incommensurate (IC) stripe order persists up to x = 0.7 in the Nd 2−x Sr x NiO 4 system, 32 in which the low temperature orthorhombic phase seems to extend to a higher doping region x ≤ 0.45 as compared to the La compounds, where the high temperature tetragonal phase is stabilized instead already at x ≃ 0.22. 1 Indications of a charge order (CO) in doped LSNO were also found in electron 33 and x-ray diffraction studies.…”

“…1,2,3,4,5,6,7,8 Moreover, the incommensurate (IC) stripe order persists up to x = 0.7 in the Nd 2−x Sr x NiO 4 system, 32 in which the low temperature orthorhombic phase seems to extend to a higher doping region x ≤ 0.45 as compared to the La compounds, where the high temperature tetragonal phase is stabilized instead already at x ≃ 0.22. 1 Indications of a charge order (CO) in doped LSNO were also found in electron 33 and x-ray diffraction studies. 34,35,36 Quite recently, the one-dimensional nature of the stripe modulation within NiO 2 planes has been directly confirmed in the transmission electron microscopy (TEM) studies of charge stripes in LSNO.…”

“…In contrast, it is clear from a variety of experiments that magnetic states within doped NiO 2 planes of the nickelates are filled stripes with density of one doped hole per one atom in a DW. 1,2,3,4,5,6,7,8 The question of filling is not the only difference between the nickelate and cuprate stripes, however. Neutron diffraction measurements performed on Nd-LSCO revealed that magnetic peaks are displaced from the antiferromagnetic (AF) maximum at Q AF = π(1, 1) to the points Q s = π(1 ± 2ǫ, 1) and Q s = π(1, 1 ± 2ǫ) and the shift ǫ depends linearly on hole doping x for x < 1/8, while it is almost constant at higher doping.…”

Electronic Raman scattering through a stripe ordering transition in La2−xSrxNiO4

“…In the first studies of La Sr NiO 2 4 -x x it has been suggested that ordering of the dopant-induced holes occurs only commensurately at special values of x, such as 1/2 and 1/3 [2,3]. Later it was found that a single crystal with x = 0.2, although not at a special value of x, shows commensurate order [6], albeit with a short in-plane correlation length of~40 Å. In contrast, the stripe order in La NiO 2 4 +d [4,5] and La 1.775 Sr 0.225 NiO 4 [7] was found to be incommensurate, with the wave vector varying significantly with temperature.…”