Magnetic phase transitions and structural distortion in Nd2CuO4

Skanthakumar, S.; Zhang, H; Clinton, T. W.; Li, Wen-Hsiung; Lynn, J. W.; Fisk, Z.; Cheong, S. W.

doi:10.1016/0921-4534(89)90180-9

Cited by 122 publications

(29 citation statements)

References 14 publications

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“…This structure is realized in Pr 2 CuO 4 and in the phases I, III of Nd 2 CuO 4 [7,[12][13][14]. The opposite direction [0,1,0] of the (1/2,1/2,1/2) spins corresponds to another structure that exists in the cuprates of Sm [8], Eu [9,10,14], Nd (phase II) [12][13][14] and results in completely different intensities of the magnetic reflections. These spin structures were explained by various models [12,15,16], but a relevant one seems to be based on the pseudodipolar interaction (PDI) postulated by Van Vleck in 1937.…”

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“…Neutron diffraction experiments in the external magnetic field applied in the [1,1,0] direction [7][8][9][10][11] have definitely proved that the copper spin subsystems are orthogonal in spite of the quan- tum effect [3]. This structure is realized in Pr 2 CuO 4 and in the phases I, III of Nd 2 CuO 4 [7,[12][13][14]. The opposite direction [0,1,0] of the (1/2,1/2,1/2) spins corresponds to another structure that exists in the cuprates of Sm [8], Eu [9,10,14], Nd (phase II) [12][13][14] and results in completely different intensities of the magnetic reflections.…”

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Quantum phase transition in Pr ₂ CuO ₄ to collinear non–spin-flop state in magnetic field: A neutron diffraction study

et al. 2003

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In the external field slightly inclined to the x-or y-axis of the frustrated tetragonal antiferromagnet Pr 2 CuO 4 , a transition is discovered from the phase with orthogonal antiferromagnetic spin subsystems along [1,0,0] and [0,1,0] to the phase with the collinear spins. This phase is shown to be due to the pseudodipolar interaction, and transforms into the spin-flop phase (S⊥H) asymptotically at very high field. The discovered phase transition holds at T = 0 and is a quantum one, with the transition field being the critical point and the angle between two subsystems being the order parameter. Rare-earth cuprates R 2 CuO 4 (R = Pr, Nd, Sm, Eu, Gd), which originally had drown attention as parent compounds for the electron-doped high-T C superconductors, now are being extensively studied as two-dimensional quantum Heisenberg antiferromagnets. These materials have a tetragonal structure with the space group I4/mmm. The CuO 2 planes give a motif of the structure, with the Cu 2+ ions being coordinated by regular squares of oxygen neighbours [1]. A very important feature of this tetragonal body-centred structure is a shift of adjacent CuO 2 planes by [1/2,1/2,1/2]. Due to very strong in-plane superexchange interaction, J = 124(3) meV [2], each Cu 2+ ion (S = 1/2) has four nearest neighbors with the opposite spins. Therefore, the mean field, produced on each copper ion by the adjacent plains is cancelled. In the absence of exchange field, the interplanar spin orientation should be very sensitive to any weak interaction that violates the symmetry. Shender [3] has shown that in a similar situation of the bcc lattice the quantum zero-point spin fluctuations stabilize a collinear orientation of the spin subsystems, which has been confirmed experimentally [4].For interpretation of the early neutron diffraction data a collinear model was used with the spins along [1,1,0] and with a propagation vector k 1 = (π/a) [1,1,0] in the same direction [5,6]. Certainly there should be another domain with the spins along [1,−1,0] and with k 2 = (π/a) [1,−1,0]. A different model with two vectors, k 1 and k 2 (2-k structure) that results in exactly the same intensities of the magnetic reflections has been also proposed [6]. In this model two antiferromagnetic subsystems are orthogonal, with the spins in positions (0,0,0) and (1/2,1/2,1/2) along [1,0,0] and [0,−1,0] directions, respectively, as shown in Fig. 1(a). Neutron diffraction experiments in the external magnetic field applied in the [1,1,0] direction [7][8][9][10][11] have definitely proved that the copper spin subsystems are orthogonal in spite of the quan-

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Quantum phase transition in Pr ₂ CuO ₄ to collinear non–spin-flop state in magnetic field: A neutron diffraction study

et al. 2003

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“…This compound is believed to be more complicated than other parent compound due to the large local moment of Eu 2+ ions. Similar to electron-type N d 2−x Ce x Cu 2 O 4−δ [16,17,18,19,20,21], the interaction between magnetic moments of Fe 2+ and Eu 2+ may lead to rich physical phenomena, and these maybe shed light to the mechanism of superconductivity in these materials. In this paper, we have studied magnetic transition by resistivity, susceptibility and specific heat in Eu 1−x La x Fe 2 As 2 single crystals.…”

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Magnetic phase diagram of single crystals

Chen

et al. 2009

Journal of Magnetism and Magnetic Materials

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We have systematically measured resistivity, susceptibility and specific heat under different magnetic fields (H) in Eu1−xLaxFe2As2 single crystals. It is found that a metamagnetic transition from A-type antiferromagnetism to ferromagnetism occurs at a critical field for magnetic sublattice of Eu 2+ . The jump of specific heat is suppressed and shifts to low temperature with increasing H up to the critical value, then shifts to high temperature with further increasing H. Such behavior supports the metamagnetic transition. Detailed H-T phase diagrams for x=0 and 0.15 crystals are given, and possible magnetic structure is proposed. Magnetoresistance measurements indicate that there exists a strong coupling between local moment of Eu 2+ and charge in Fe-As layer. These results are very significant to understand the underlying physics of FeAs superconductors. The discovery of superconductivity [1, 2,3,4] in ironpnicitides LnF eAsO 1−x F x (Ln=La, Sm, Ce and Pr) has generated much interest for extensive study on such iron-based superconductors, which is the second family of high-T c superconductors except for the high-T c cuprates. The magnetic ordering of the rare earth ions Ln 3+ at low temperature has been observed by neutron scattering [5,6,7] except for the spin density wave arose from F e 2+ . The coupling between Ln 3+ and Fe 2+ has been found above ordering temperature for local moment of rare earth ions Ln 3+ [5]. These results indicate that the coupling between spins of rare earth ions and Fe 2+ ions seems to be one important ingredient to understand magnetic properties at low temperatures. It is well known that spin density wave (SDW) is suppressed, while superconductivity emerges with doping [8,9,10,11,12]. However, no evidence is given for how to couple between SDW and magnetic ordering of rare earth ions Ln 3+ , and effect of magnetic ordering of Ln 3+ on superconductivity. Therefore, the coupling between the SDW from F e 2+ and magnetic ordering of rare earth ions Ln 3+ should be a very interesting issue. It maybe shed light to understand the underlying physics in Fe-As compounds.EuFe 2 As 2 is one of parent compounds with T hCr 2 Si 2 -type structure. It shows a SDW transition around 190 K, and an antiferromagnetic transition of Eu 2+ ions occurs at T N ∼20 K [13]. Superconductivity at ∼ 30 K can be achieved by K or Na doping [14,15]. This compound is believed to be more complicated than other parent compound due to the large local moment of Eu 2+ ions. Similar to electron-type N d 2−x Ce x Cu 2 O 4−δ [16,17,18,19,20,21], the interaction between magnetic moments of Fe 2+ and Eu 2+ may lead to rich physical phenomena, and these maybe shed light to the mechanism of superconductivity in these materials. In this paper, we have studied magnetic transition by resistivity, susceptibility and specific heat in Eu 1−x La x Fe 2 As 2 single crystals. The magnetic structure of Eu 2+ ions is found to be strongly dependent on external magnetic field. A metamagnetic transition from A-type antiferromagnetism to ferro...

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“…In fact we show that for any other spin orientation direct spin-flip scattering is allowed. This includes in particular the Néel ordered high T c cuprates, where the magnetic moment lies in the plane of the [20] The dependence of the direct spin-flip scattering amplitude on photon polarization, scattering angle and momentum transfer can be computed from the Kramers-Heisenberg expression [21]:…”

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Theoretical Demonstration of How the Dispersion of Magnetic Excitations in Cuprate Compounds can be Determined Using Resonant Inelastic X-Ray Scattering

et al. 2009

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We show that, contrary to common lore, in resonant inelastic x-ray scattering (RIXS) at the copper L-and M-edge direct spin-flip scattering is in principle allowed. We demonstrate how this possibility can be exploited to probe the momentum dependent magnetic properties of cuprates such as the high Tc superconductors and compute in detail the relevant local and momentum dependent magnetic scattering amplitudes, which we compare to the elastic and dd-excitation scattering intensities. For cuprates these results put RIXS as a technique on the same footing as neutron scattering.Introduction. In recent years the experimental technique of resonant inelastic x-ray scattering (RIXS) has made tremendous progress in terms of energy and momentum resolution [1,2,3,4,5,6,7,8,9,10,11]. RIXS is particularly apt to probe the properties of strongly correlated electrons, for instance the ones of the transition metal oxides [1,2]. With an incoming x-ray of energy ω in first an electron is resonantly excited from a core level into the valence shell. Subsequently one measures the energy ω out of the outgoing x-ray resulting from the recombination of the core hole with a valence electron. Depending on the resonance that the experiment is performed at, ω in corresponds to the transition metal K-edge (1s → 4p), L-edge (2p → 3d) or M-edge (3p → 3d). Compared to the many other photon scattering techniques, RIXS has the advantage that there is no core hole present in the final state, so that the energy lost by the scattered photon at a transition metal L-or M-edge is directly related to electronic excitations within the strongly correlated 3d valence bands. The chemical selectivity and bulk sensitivity of RIXS allows the study of the electronic and magnetic properties of, for example, complex and nanostructured materials that might be inaccessible with non-resonant techniques.

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Magnetic phase transitions and structural distortion in Nd2CuO4

Cited by 122 publications

References 14 publications

Quantum phase transition in Pr ₂ CuO ₄ to collinear non–spin-flop state in magnetic field: A neutron diffraction study

Quantum phase transition in Pr ₂ CuO ₄ to collinear non–spin-flop state in magnetic field: A neutron diffraction study

Magnetic phase diagram of single crystals

Theoretical Demonstration of How the Dispersion of Magnetic Excitations in Cuprate Compounds can be Determined Using Resonant Inelastic X-Ray Scattering

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Magnetic phase transitions and structural distortion in Nd2CuO4

Cited by 122 publications

References 14 publications

Quantum phase transition in Pr 2 CuO 4 to collinear non–spin-flop state in magnetic field: A neutron diffraction study

Quantum phase transition in Pr 2 CuO 4 to collinear non–spin-flop state in magnetic field: A neutron diffraction study

Magnetic phase diagram of single crystals

Theoretical Demonstration of How the Dispersion of Magnetic Excitations in Cuprate Compounds can be Determined Using Resonant Inelastic X-Ray Scattering

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Quantum phase transition in Pr ₂ CuO ₄ to collinear non–spin-flop state in magnetic field: A neutron diffraction study

Quantum phase transition in Pr ₂ CuO ₄ to collinear non–spin-flop state in magnetic field: A neutron diffraction study