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Sr
MnO
Kajimoto, Ryoichi; Yoshizawa, Hideki*; Kawasaki, Ryuichi*; Noda, Kohei*; Kuwahara, Hideki*
Journal of the Physical Society of Japan, 74(1), p.502 - 503, 2005/01
Times Cited Count：2 Percentile：19.48(Physics, Multidisciplinary)The spin wave dispersion relation of the C-type antiferromagnetic structure in Nd
Sr
MnO was determined by neutron scattering. The spin exchange interactions show a large anisotropy, which evidences the d
orbital ordering along the 
axis. The exchange interaction along the direction is fairly large and similar to the value in the ferromagnetic metallic phase, suggesting there is finite hopping of charges along the orbital chains.
Ueda, Kazuo; Hotta, Takashi
JAERI-Review 2002-037, 31 Pages, 2002/12
JAERI-Review-2002-037.pdf:2.7MB
Strongly correlated f- and d-electron systems including heavy Fermion systems and transition metal oxides are important source of exciting new phenomena in condensed matter physics. Recently it has been recognized in more profound way that the orbital degeneracy of the f- and d-electrons plays very important role underlying those exotic phenomena. The idea of the present workshop is to bring active researchers in the field together and to exchange ideas in informal atmosphere. In the workshop many interesting results were presented and stimulating discussions were made as clearly seen by the present report.
Hotta, Takashi; Dagotto, E.*
Physica B; Condensed Matter, 312-313(1-4), p.700 - 702, 2002/03
Times Cited Count：2 Percentile：14.16(Physics, Condensed Matter)The crucial role of the orbital degree of freedom is here discussed in order to understand the complex spin and charge structures of transition metal oxides. For manganites, it is shown that diagonal charge stripes in the ferromagnetic phase are induced by the staggered orbital ordered pattern, while for ruthenates, a novel orbital ordering is found to exist in the G-type antiferromagnetic structure, with a hole arrangement as recently observed in X-ray experiments.
Hotta, Takashi; Dagotto, E.*
Physical Review Letters, 88(1), p.017201_1 - 017201_4, 2002/01
Times Cited Count：81 Percentile：89.89(Physics, Multidisciplinary)The key role of the orbital degree of freedom to understand the magnetic properties of layered ruthenates is here discussed. In the G-type antiferromagnetic (AFM) phase of Ca
RuO
, recent X-ray experiments reported the presence of 0.5 hole per site in the 
orbital, while the 
and 
orbitals contain 1.5 holes. This unexpected 
hole distribution is explained by a novel state with orbital ordering (OO), stabilized by a combination of Coulomb interactions and lattice distortions. In addition, the rich phase diagram presented here suggests the possibility of large magnetoresistance effects, and predicts a new ferromagnetic OO phase in ruthenates.
