Separation of Quadrupolar and Magnetic Contributions to Spin–Lattice Relaxation in the Case of a Single Isotope

Suter, A.; Mali, M.; Roos, J.; Brinkmann, D.

doi:10.1006/jmre.1999.1990

Cited by 12 publications

(7 citation statements)

References 22 publications

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“…Phonons will cause nuclear relaxation for quadrupolar nuclei (I > 1/2, like Cu and O) as they modulate the electric field gradient, but it has been shown that the magnetic fluctuations dominate in most situations [ 20,21], and the recent analysis of all Cu relaxation data shows that a simple magnetic mechanism appears to capture the overall behavior quite well [16,17].…”

Section: Planar Cu Relaxationmentioning

confidence: 99%

NMR Shift and Relaxation and the Electronic Spin of Superconducting Cuprates

Avramovska

Pavićević

Haase

2020

J Supercond Nov Magn

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Very recently, there has been significant progress with establishing a common phenomenology of the superconducting cuprates in terms of nuclear magnetic resonance (NMR) shift and relaxation. Different from the old interpretation, it was shown that the shifts demand two coupled spin components with different temperature dependencies. One spin component couples isotropically to the planar Cu nucleus and is likely to reside at planar O, while the other, anisotropic component has its origin in the planar copper 3d(x 2 − y 2 ) orbital. Nuclear relaxation, on the other hand, was found to be rather ubiquitous and Fermi liquid-like for planar Cu, i.e., it is independent of doping and material, apart from the sudden drop at the superconducting transition temperature, Tc. However, there is a doping and material dependent anisotropy that is independent on temperature, above and below Tc. Here we present a slightly different analysis of the shifts that fits all planar Cu shift data. In addition we are able to derive a simple model that explains nuclear relaxation based on these two spin components. In particular, the only outlier so far, La2−xSrxCuO4, can be understood, as well. While this concerns predominantly planar Cu, it is argued that the two component model should fit all cuprate shift and relaxation data.March 25, 2020 ⊥ arXiv:2002.09903v2 [cond-mat.supr-con]

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Section: Planar Cu Relaxationmentioning

confidence: 99%

NMR Shift and Relaxation and the Electronic Spin of Superconducting Cuprates

Avramovska

Pavićević

Haase

2020

J Supercond Nov Magn

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“…Thus, for a static field H 0 [001] HTT , the quantity 63 (T 1 T ) −1 reflects the weighted q average of χ"(q, ω 0 ), the imaginary part of the in-plane dynamical spin susceptibility at the frequency ω 0 . The magnetization recovery curves for 63 Cu were therefore fitted to the standard expression [20] for a purely magnetic relaxation over the entire temperature range investigated assuming a single T 1 . The temperature dependence of 63 (T 1 T ) −1 is shown in Fig.…”

mentioning

confidence: 99%

Experimental evidence for a glass forming stripe liquid in the magnetic ground state ofLa1.65Eu0.2Sr

et al. 2003

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We report measurements of the longitudinal ( 139 T −1 1 ) and transverse ( 139 T −1 2 ) decay rates of the magnetization of 139 La nuclei performed in a high quality single crystal of La1.65Eu0.2Sr0.15CuO4. We observe a dramatic slowing of the Cu 3d spins manifested as a sharp increase of both 139 T −1 1 and 139 T −1 2 below 30 K. We find that in this temperature range the fluctuations involve a unique time scale τ which diverges as (T − TA) −1.9 with TA ≈ 5 K. This behavior is distinct from the continuous freezing observed in underdoped La1−xSrxCuO4 which involves a distribution of energy barriers. By contrast, in La1.65Eu0.2Sr0.15CuO4, the freezing below 30K is intrinsic to its magnetic ground state and the observed power law supports the existence of a glass forming "charge stripe liquid".Charge inhomogeneities in doped transition metaloxides have aroused great interest because of their possible implication in superconductivity. Indeed, it has been proposed [1,2,3,4] that the superconducting state in underdoped cuprates may consist of a charge stripe phase, in which hole-rich fluctuating stripes act as antiphase boundaries between undoped antiferromagnetic (AF) domains. Experimentally, the presence of a stripe order was inferred from elastic neutron scattering measurements [5] in compounds that are not superconducting: doped lanthanum nickelates and the rare earth codoped lanthanum cuprate La 1.48 Nd 0.4 Sr 0.12 CuO 4 . In the latter, the substitution for La ions by isovalent rare earth ions (Nd or Eu) induces a structural transition from the low temperature orthorhombic (LTO) to the low temperature tetragonal (LTT) phase in which a magnetic ground state occurs in lieu of the superconducting state [6].In both structures, LTO and LTT, the CuO 6 octahedra are tilted inducing a staggered buckling of the CuO 2 plane [7]. The difference between the two phases consists only of a rotation of the tilt axis from [110] HTT in the LTO phase to [100] HTT or [010] HTT alternating along the c axis in the LTT phase. Though specific to lanthanum cuprates, the LTT structure was shown [6,8] to have the remarkable property of generating either a magnetic or superconducting ground state with similar critical temperature at fixed optimal Sr 2+ doping (x=0.15) depending only on the amplitude of the buckling, controlled by the Eu or Nd concentration. This suggests the same physics underlies the two outcomes, but little is known about the fundamental mechanism that connects them. In this context, it is important to gain further insight into the low energy properties of the magnetic ground state in rare earth co-doped lanthanum cuprates.In this Letter, we report NMR measurements performed on 63 Cu and 139 La nuclei in a La 1.65 Eu 0.2 Sr 0.15 CuO 4 single crystal. For the first time, we investigate the slowing down of the Cu 3d spins in this compound by measuring two relaxation rates: 139 T −1 1 and 139 T −1 2 . For a given orientation of the crystal in a static field H 0 , T −1 1 probes the spectral weight of the transverse fluctuati...

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“…When T 1Q1 is only slightly larger than T 1Q2 (4 s vs. 3 s) the calculated recovery curve appears to be reasonably close to single-exponential; forcing a fit of this curve to a single-exponential gives a time constant T 1 ("T 1Q1 = T 1Q2 ) = 2.2 s. The expanded difference plot shows that the calculated recovery curve agrees within a couple of percent of that for a single-exponential; however, the corresponding time constants are substantially different, with T 1Q1 , T 1Q2 > T 1 . These simulations clearly demonstrate that even though experimental relaxation curves may closely approximate single-exponential recovery, Table 1 Experimental conditions for saturation-recovery measurements (see Ga, magic-angle (0) 6 Not achievable (0) 6 (5.4) n a 90°pulse for CT = 12.5 ls. b CT inadvertently excluded from list; nevertheless, CT saturation measured to be 89% of full saturation, with negligible calculated effects on recovery curves.…”

Section: General Strategymentioning

confidence: 95%

“…The description of spin-lattice relaxation in multilevel systems of half-integral quadrupolar nuclei dates back a half century to Pound's original work [1]. Subsequent studies have emphasized solutions to the set of coupled rate equations describing the populations of each level [2][3][4][5][6]. These solutions depend upon both the initial state of the spin system in a given T 1 experiment, as well as the nature of the relaxation mechanism (viz., whether quadrupolar or magnetic in nature).…”

Section: Introductionmentioning

confidence: 99%

Magnetization-recovery experiments for static and MAS-NMR of I=3/2 nuclei

Yesinowski

2006

Journal of Magnetic Resonance

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Separation of Quadrupolar and Magnetic Contributions to Spin–Lattice Relaxation in the Case of a Single Isotope

Cited by 12 publications

References 22 publications

NMR Shift and Relaxation and the Electronic Spin of Superconducting Cuprates

NMR Shift and Relaxation and the Electronic Spin of Superconducting Cuprates

Experimental evidence for a glass forming stripe liquid in the magnetic ground state ofLa1.65Eu0.2Sr

Magnetization-recovery experiments for static and MAS-NMR of I=3/2 nuclei

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