Spin and orbital contributions to magnetically ordered moments in 5d layered perovskite Sr2IrO4.
The ratio of orbital (L) and spin (S) contributions to the magnetically ordered moments of a 5d transition metal oxide, Sr2IrO4 was evaluated by nonresonant magnetic x-ray diffraction. We applied an improved experimental setting that minimized the experimental error, in which we varied only the linear polarization of incident x ray at a fixed scattering angle. Strong polarization dependence of the intensity of magnetic diffraction was observed, from which we conclude that the ordered moments contain substantial contribution from the orbital degree of freedom with the ratio of <L>/<S>∼5.0, evidencing the pronounced effect of spin-orbit coupling. The obtained ratio is close to, but slightly larger than the expected value for the ideal J(eff) = 1/2 moment of a spin-orbital Mott insulator, |<J(1/2)|L(z)|J(1/2)>|/|<J(1/2)|S(z)|J(1/2)>| = 4, which cannot be accounted for by the redistribution of orbital components within the t(2g) bands associated with the elongation of the IrO6 octahedra.
RIKEN, Magnetic Materials Laboratory, Wako 351-0198, Japan.
S
S
Fujiyama
RIKEN, SPring-8 Center, Sayo, Hyogo 679-5148, Japan.
H
H
Ohsumi
Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan.
K
K
Ohashi
Department of Physics, University of Tokyo, Tokyo 113-0033, Japan.
D
D
Hirai
Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan.
B J
BJ
Kim
RIKEN, SPring-8 Center, Sayo, Hyogo 679-5148, Japan and Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan.
T
T
Arima
RIKEN, SPring-8 Center, Sayo, Hyogo 679-5148, Japan.
M
M
Takata
RIKEN, Magnetic Materials Laboratory, Wako 351-0198, Japan and Department of Physics, University of Tokyo, Tokyo 113-0033, Japan.
H
H
Takagi