Electron Spin Resonance in the Spin-1/2Quasi-One-Dimensional Antiferromagnet with Dzyaloshinskii-Moriya InteractionBaCu

Abstract

We have investigated the electron spin resonance (ESR) on single crystals of BaCu2Ge2O7 at temperatures between 300 and 2 K and in a large frequency band, 9.6 -134 GHz, in order to test the predictions of a recent theory, proposed by Oshikawa and Affleck (OA), which describes the ESR in a S=1/2 Heisenberg chain with the Dzyaloshinskii-Moriya interaction. We find, in particular, that the ESR linewidth, ∆H, displays a rich temperature behavior. As the temperature decreases from Tmax/2 ≈ 170 K to 50 K, ∆H shows a rapid and linear decrease, ∆H ∼ T . At low temperatures, below 50 K, ∆H acquires a strong dependence on the magnetic field orientation and for H c it shows a (h/T ) 2 behavior which is due to an induced staggered field h, according to OA's prediction.

Site-selective quantum correlations revealed by magnetic anisotropy in the tetramer system SeCuO3

“…In SeCuO 3 there are two copper sites, Cu1 and Cu2, with different values and orientations of their g tensors. Since they are exchangecoupled, the ESR experiment observes only one line with a total g tensor which nontrivially depends on g 1 , g 2 , J 11 , and J 12 (to a lesser extent even on J 22 ). From the present set of data we are not able to fully model the system.…”

“…(2) can reproduce the susceptibility in the range 10 K < T < 70 K. Considering the structural arguments presented in Sec. III A, it is natural to assume that the crossover is a consequence of the intertetramer interaction along the a axis, J 22 . It is expected that this interaction is rather weak compared to J 11 and J 12 due to the large elongation of the Cu2 octahedron [d(Cu2-O4) = 2.71Å].…”

“…It is expected that this interaction is rather weak compared to J 11 and J 12 due to the large elongation of the Cu2 octahedron [d(Cu2-O4) = 2.71Å]. However, since the octahedron is not ideal, there may be some mixing of d x 2 −y 2 and d 3z 2 −r 2 orbitals in the Cu2-O4 coupling, allowing for a finite J 22 . The value of the angle (Cu2-O4-Cu2) = 95…”

“…Such a change can come from a lateral shift of the O4 apical ion relative to the d x 2 −y 2 orbital, thus pulling the neighboring tetramers closer along the a axis. However, this also reduces the distortion of the Cu2 octahedron which implies a smaller contribution from active d x 2 −y 2 orbitals and consequently a smaller J 22 . In order to clarify this issue, further structural and theoretical studies are needed.…”

“…One is along the a axis between two Cu2 ions on the neighboring tetramers, J 22 , and incorporates the d 3z 2 −r 2 orbital. Since the octahedron is not ideal, there may be some mixing between d 3z 2 −r 2 and d x 2 −y 2 orbitals, giving rise to a finite J 22 . The second intertetramer interaction is the interchain interaction J and it is mediated via Cu-O-Se-O-Cu paths.…”