TY - JOUR
T1 - Spin and charge orders and their hole-doping dependence in single layered cobaltate La 2-xCa xCoO 4 (0.3 ≦ x ≦ 0.8)
AU - Horigane, Kazumasa
AU - Hiraka, Haruhiro
AU - Uchida, Toru
AU - Yamada, Kazuyoshi
AU - Akimitsu, Jun
PY - 2007/11
Y1 - 2007/11
N2 - Neutron scattering experiments were performed on single crystals of layered cobalt-oxides La 2-xCa x-CoO 4 (LCCO) to characterize the charge and spin orders in a wide hole-doping range of 0.3 ≦ x ≦ 0.8. For a commensurate value of x = 0.5 in (H, 0, L) plane, two types of superlattice reflections concomitantly appear at low temperature; one corresponds to a checkerboard charge ordered pattern of Co 2+/ Co 3+ ions and the other is magnetic in origin. Further, the latter magnetic-superlattice peaks show two types of symmetry in the reflections, suggesting antiferromagnetic-stacking (AF-S) and ferromagnetic-stacking (F-S) patterns of spins along the c direction. From the hole-doping dependence, the in-plane correlation lengths of both charge and spin orders are found to give a maximum at x = 0.5. These features are the same with those of x = 0.5 in La i-xSr 1+xMnO 4 (LSMO), a typical checkerboard and spin ordered compound. However, in (H, H, L) plane, we found a magnetic scattering peak at Q = (0.25,0.25,0.5) position below T N. This magnetic peak can not be understood by considering the Co 2+ spin configuration, suggesting that this peak is originated from Co 3+ spin order. By analyzing these superlattice reflections, we found that they are originated from high-spin state of Co 3+ spin order.
AB - Neutron scattering experiments were performed on single crystals of layered cobalt-oxides La 2-xCa x-CoO 4 (LCCO) to characterize the charge and spin orders in a wide hole-doping range of 0.3 ≦ x ≦ 0.8. For a commensurate value of x = 0.5 in (H, 0, L) plane, two types of superlattice reflections concomitantly appear at low temperature; one corresponds to a checkerboard charge ordered pattern of Co 2+/ Co 3+ ions and the other is magnetic in origin. Further, the latter magnetic-superlattice peaks show two types of symmetry in the reflections, suggesting antiferromagnetic-stacking (AF-S) and ferromagnetic-stacking (F-S) patterns of spins along the c direction. From the hole-doping dependence, the in-plane correlation lengths of both charge and spin orders are found to give a maximum at x = 0.5. These features are the same with those of x = 0.5 in La i-xSr 1+xMnO 4 (LSMO), a typical checkerboard and spin ordered compound. However, in (H, H, L) plane, we found a magnetic scattering peak at Q = (0.25,0.25,0.5) position below T N. This magnetic peak can not be understood by considering the Co 2+ spin configuration, suggesting that this peak is originated from Co 3+ spin order. By analyzing these superlattice reflections, we found that they are originated from high-spin state of Co 3+ spin order.
KW - Checkerboard charge order
KW - Cobalt oxide
KW - Neutron diffraction
KW - Spin and charge order
KW - Spin state of Co
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U2 - 10.1143/JPSJ.76.114715
DO - 10.1143/JPSJ.76.114715
M3 - Article
AN - SCOPUS:36148980510
VL - 76
JO - Journal of the Physical Society of Japan
JF - Journal of the Physical Society of Japan
SN - 0031-9015
IS - 11
M1 - 114715
ER -