摘要 :
We present elastic and inelastic neutron scattering data on LaSrFeO_4. We confirm the known magnetic structure with the magnetic moments lying in the tetragonal basal plane, but our macroscopic and neutron diffraction data do not ...
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We present elastic and inelastic neutron scattering data on LaSrFeO_4. We confirm the known magnetic structure with the magnetic moments lying in the tetragonal basal plane, but our macroscopic and neutron diffraction data do not reveal any additional magnetic phase transition connected to a spin reorientation or to a redistribution of two irreducible representations. Our inelastic neutron scattering data reveals the magnon dispersion along the main-symmetry directions [0 ξ 0] and [ξ -ξ 0], The dispersion can be explained within linear spin-wave theory yielding an antiferromagnetic nearest-neighbor interaction parameter J_1 = 7.4(3) meV and a next-nearest neighbor interaction parameter J_2 = 0.4(3) meV. The dispersion is gapped with the out-of-plane anisotropy gap found at Δ_(out) = 5.26(2) meV, while evidence is present that the in-plane anisotropy gap lies at lower energies, where it cannot be determined due to limited instrument resolution.
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摘要 :
Inelastic neutron-scattering experiments have been performed on lightly doped La_(1.96)Sr_(0.04)CuO_4, which shows diagonal incommensurate spin correlations at low temperatures. We previously reported that this crystal, with a sin...
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Inelastic neutron-scattering experiments have been performed on lightly doped La_(1.96)Sr_(0.04)CuO_4, which shows diagonal incommensurate spin correlations at low temperatures. We previously reported that this crystal, with a single orthorhombic domain, exhibits the "hourglass" dispersion at low energies [Phys. Rev. Lett. 101, 197001 (2008)]. In this paper, we investigate in detail the energy evolution of the magnetic excitations up to 65 meV. It is found that the anisotropic excitations at low energies, dispersing only along the spin modulation direction, cross over to an isotropic, conical dispersion that resembles spin waves in the parent compound La_2CuO_4. The change from twofold to full symmetry on crossing the waist of the hourglass reproduces behavior first identified in studies of underdoped YBa_2Cu_3O_(6+x). We discuss the significance of these results.
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摘要 :
We calculate the temperature dependence of the correlation length ξ and the uniform susceptibility X_0 of the frustrated J_1-J_2 square-lattice Heisenberg ferromagnet in the collinear stripe phase using the Green-function techniq...
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We calculate the temperature dependence of the correlation length ξ and the uniform susceptibility X_0 of the frustrated J_1-J_2 square-lattice Heisenberg ferromagnet in the collinear stripe phase using the Green-function technique. The height X_max and the position T(x_max) of the maximum in the X_0(T) curve exhibit a characteristic dependence on the frustration parameter J_2/|J_1|, which is well described, for J_2 > 0.7|J_1|, by the relations Xmax = a(J_2 - J_2~c )~v and T(X_max) = b(J_2 - J_2~c), where J_2~C = 0.4|J_1| and v is of the order of unity. The correlation length diverges at low temperatures as ξ ∝ e~(A/T), where A increases with growing J_2/|J_1|. We also compare our results with recent measurements on layered oxovanadates and find reasonable agreement.
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