Soft phonon behavior and magnetism at the low temperature structural phase transition of La1.65Nd0.35CuO4

Keimer, B.; Birgeneau, R. J.; Cassanho, A.; Endoh, Y.; Greven, M.; Kastner, M. A.; Shirane, G.

doi:10.1007/bf01344067

Cited by 100 publications

(106 citation statements)

References 24 publications

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“…72 Since H c1 is a measure of the in-plane gap, our results suggest that in the LTLO phase the effective in-plane gap decreases, which is in contradiction to the increase reported in Ref. 9 (details in discussion).…”

contrasting

confidence: 67%

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrx
Hücker
¹
,
Kataev
²
,
Pommer
³

et al. 2004
Phys. Rev. B

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The Cu spin magnetism in La2−x−yEuySrxCuO4 (x ≤ 0.17; y ≤ 0.2) has been studied by means of magnetization measurements in fields up to 14 Tesla. Our results clearly show that in the antiferromagnetic phase Dzyaloshinsky-Moriya (DM) superexchange causes Cu spin canting not only in the LTO phase but also in the structural low-temperature phases LTLO and LTT. In La1.8Eu0.2CuO4 the canted DM-moment is about 50% larger than in pure La2CuO4 which we attribute to the larger octahedral tilt angle in the Eu-doped compound. We also find clear evidence that the size of the canted DM-moment does not change significantly at the structural transition at TLT from LTO to LTLO and LTT. The most important change induced by the transition is a significant reduction of the magnetic coupling between the CuO2 planes. As a consequence, the spin-flip transition of the canted Cu spins which is observed in the LTO phase for magnetic field perpendicular to the CuO2 planes disappears in the LTT phase. The shape of the magnetization curves changes from the well known spin-flip type to a weak-ferromagnet type. However, no spontaneous weak ferromagnetism is observed even at very low temperatures, which seems to indicate that the interlayer decoupling in our samples is not perfect. Nonetheless, a small fraction ( 15%) of the DM-moments can be remanently magnetized throughout the entire antiferromagnetically ordered LTT/LTLO phase, i.e. for T < TLT and x < 0.02. It appears that the remanent DM-moment is perpendicular to the CuO2 planes. For magnetic field parallel to the CuO2 planes we find that the critical field of the spin-flop transition decreases in the LTLO phase, which might indicate a competition between different inplane anisotropies. To study the Cu spin magnetism in La2−x−yEuySrxCuO4, a careful analysis of the Van Vleck paramagnetism of the Eu 3+ ions was performed.

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contrasting

confidence: 67%

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrx
Hücker
¹
,
Kataev
²
,
Pommer
³

et al. 2004
Phys. Rev. B

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“…On the other hand, Hess et al [14] pointed out that one cannot exclude that subtle structural effects unrelated to electronic order are the actual cause of the slight enhancement at T ν . For example, soft phonon type precursors of the LTO → LTT transition are known to be ubiquitous in the LTO phase of both La 2−x−y RE y Sr x CuO 4 (RE=Rare Earth), which undergoes the LTO → LTT transition, and La 2−x Sr x CuO 4 , which remains in the LTO phase down to lowest temperature [62,63,64]. In fact, this conjecture is supported by the jump-like response of the Nernst coefficient at T LT for the lower doping levels.…”

Section: Nernst Effect and Sdw Fluctuations In The Iron-based Supercomentioning

confidence: 99%

Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe Order

Heß

2012

NATO Science for Peace and Security Series B: Physics and Biophysics

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The Nernst effect has recently proven a sensitive probe for detecting unusual normal state properties of unconventional superconductors. In particular, it may sensitively detect Fermi surface reconstructions which are connected to a charge or spin density wave (SDW) ordered state, and even fluctuating forms of such a state. Here we summarize recent results for the Nernst effect of the iron pnictide superconductor LaO 1−x F x FeAs, whose ground state evolves upon doping from an itinerant SDW to a superconducting state, and the cuprate superconductor La 1.8−x Eu 0.2 Sr x CuO 4 which exhibits static stripe order as a ground state competing with the superconductivity. In LaFeAsO 1−x F x , the SDW order leads to a huge Nernst response, which allows to detect even fluctuating SDW precursors at superconducting doping levels where long range SDW order is suppressed. This is in contrast to the impact of stripe order on the normal state Nernst effect in La 1.8−x Eu 0.2 Sr x CuO 4 . Here, though signatures of the stripe order are detectable in the temperature dependence of the Nernst coefficient, its overall temperature dependence is very similar to that of La 2−x Sr x CuO 4 , where stripe order is absent. The anomalies which are induced by the stripe order are very subtle and the enhancement of the Nernst response due to static stripe order in La 1.8−x Eu 0.2 Sr x CuO 4 as compared to that of the pseudogap phase in La 2−x Sr x CuO 4 , if any, is very small.

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“…24,25,26 The latter magnetic structure is shown in Fig. 1 (c), where spins are perpendicular to the rotation axes of the CuO 6 octahedra, and thus the spin canting remains intact.…”

mentioning

confidence: 93%

Significant suppression of weak ferromagnetism in(La1.8Eu0.2)CuO
Tsukada
¹
,
Sun
²
,
Komiya
³

et al. 2003
Phys. Rev. B
14
3
19
1
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The magnetic structure of (La 1.8 Eu 0.2 )CuO 4 has been studied by magnetization measurements of single crystals, which show antiferromagnetic long-range order below T N = 265 K and a structural phase transition at T s = 130 K. At T s < T < T N , the Cu spin susceptibility exhibits almost the same behavior as that of La 2 CuO 4 in the low-temperature orthorhombic phase, which indicates the existence of finite spin canting out of the CuO 2 plane. At T < T s , the magnitude of the weak-ferromagnetic moment induced by the spin canting is suppressed approximately by 70%. This significant suppression of the weak-ferromagnetic moment is carefully compared with the theoretical analysis of weak ferromagnetism by Stein et al. (Phys. Rev. B 53, 775 (1996)), in which the magnitude of weak-ferromagnetic moments strongly depend on the crystallographic symmetry. Based on such comparison, below T s (La 1.8 Eu 0.2 )CuO 4 is in the low-temperature lessorthorhombic phase with a space group of P ccn. We also discuss the possible magnetic structure of the pure low-temperature tetragonal phase with space group P 4 2 /ncm, which is relevant for rare-earth and alkaline-earth ions co-doped La 2 CuO 4 . 15 He reinvestigated the role of spin-orbit interaction in super-exchange mechanism for one-dimensional S = 1/2 antiferromagnetic (AF) spin chains and spin rings, and found that the anisotropic symmetric interaction gives an easy-axis anisotropy to the spin system that completely compensates the easy-plane anisotropy given by the DM interaction. One possible test is to determine the magnetic structure of the so-called low-temperature tetragonal (LTT) phase (space group P 4 2 /ncm), which was first reported in (La,Ba) 2 CuO 4 . 20Bonesteel 12 discussed that the weak-ferromagnetic (WF) moment per CuO 2 plane should disappear in the LTT phase as is schematically drawn in Fig. 1 (b) when one takes the KSEA interaction into account. In this arrangement, spins are parallel to the rotation axes of CuO 6 octahedra, and therefore, they are also parallel/antiparallel to the DM vectors.This theoretical prediction became a trigger of a long debate, 21,22,23 because the magnetic structure shown in Fig. 1 (b) was different from that proposed based on neutron diffraction

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Soft phonon behavior and magnetism at the low temperature structural phase transition of La1.65Nd0.35CuO4

Cited by 100 publications

References 24 publications

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrx
Hücker
¹
,
Kataev
²
,
Pommer
³

et al. 2004
Phys. Rev. B

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrx
Hücker
¹
,
Kataev
²
,
Pommer
³

et al. 2004
Phys. Rev. B

Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe Order

Significant suppression of weak ferromagnetism in(La1.8Eu0.2)CuO
Tsukada
¹
,
Sun
²
,
Komiya
³

et al. 2003
Phys. Rev. B
14
3
19
1
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Soft phonon behavior and magnetism at the low temperature structural phase transition of La1.65Nd0.35CuO4

Cited by 100 publications

References 24 publications

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrxHücker1, Kataev2, Pommer3 et al. 2004Phys. Rev. B

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrxHücker1, Kataev2, Pommer3 et al. 2004Phys. Rev. B

Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe Order

Significant suppression of weak ferromagnetism in(La1.8Eu0.2)CuOTsukada1, Sun2, Komiya3 et al. 2003Phys. Rev. B143191View full textAdd to dashboardCite

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Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrx
Hücker
¹
,
Kataev
²
,
Pommer
³

et al. 2004
Phys. Rev. B

Dzyaloshinsky-Moriya spin canting in the low-temperature tetragonal phase ofLa2−x−yEuySrx
Hücker
¹
,
Kataev
²
,
Pommer
³

et al. 2004
Phys. Rev. B

Significant suppression of weak ferromagnetism in(La1.8Eu0.2)CuO
Tsukada
¹
,
Sun
²
,
Komiya
³

et al. 2003
Phys. Rev. B
14
3
19
1
View full text Add to dashboard Cite