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Dipolar nuclear polarization via the spin diffusion of a dipole order. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 320:106847. [PMID: 33096373 DOI: 10.1016/j.jmr.2020.106847] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/01/2020] [Accepted: 10/07/2020] [Indexed: 06/11/2023]
Abstract
We propose transfer of the paramagnetic impurity (PI) polarization to nuclei in bulk, outside the diffusion barrier, by using dipolar system of the nuclear spins. The transfer can overcome influence of the diffusion barrier and is proposed to be implemented in four stages. At the first stage, transition of the Zeeman PI order to the Zeeman order of nuclear spins inside the spin-diffusion barrier is occurred. During the second stage the Zeeman order of both the nuclear spins inside the barrier and the nuclear spins in bulk is transferred into the nuclear dipolar spin order. As a result, the nuclear dipolar spin reservoir inside the barrier acquires a lower spin temperature, and thus a gradient of the spin temperature of the nuclear dipolar spin system is created. Since the external magnetic field and the magnetic field created by PIs do not effect on the dipole-dipole interaction between the nuclear spins, the dipolar reservoir is common for all nuclear spins, both inside and outside the diffusion barrier. Restriction of the diffusion barrier is removed and the spin diffusion of the dipole energy and transfer of the spin dipolar order to bulk spins occurs without obstacles (the third stage). At the last stage, to register an NMR signal, the dipolar order of the bulk spins is transferred into the Zeeman order of these spins. Estimations show that enhancement of the polarization can reaches in the case of a 1H nuclear spin, ~220, for 13C ~850, and for 15N ~2130.
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Location of paramagnetic defects in detonation nanodiamond from proton spin-lattice relaxation data. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2020; 105:101624. [PMID: 31731104 DOI: 10.1016/j.ssnmr.2019.101624] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/22/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
We developed an approach for determining location of intrinsic paramagnetic defects in nanodiamonds from the data of proton spin-lattice relaxation of the surface hydrogen atoms. The approach was applied to the detonation nanodiamond (DND) of the diameter of 5 nm. We found that dangling bonds with unpaired electron spins are located within the near-surface belt at the distance of 0.3-0.9 nm from the DND surface. The NMR data are compared with the results of EPR measurements.
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(13)C spin-lattice relaxation in nanodiamonds in static and magic angle spinning regimes. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2015; 66-67:51-55. [PMID: 25465482 DOI: 10.1016/j.ssnmr.2014.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 10/08/2014] [Accepted: 10/10/2014] [Indexed: 06/04/2023]
Abstract
We report on (13)C nuclear spin-lattice relaxation time (T1) dependence on the magic-angle-spinning (MAS) rate in powder nanodiamond samples. We confirm that the relaxation is caused by interaction of nuclear spins with fluctuating electron spins of localized paramagnetic defects. It was found that T1 is practically not affected by MAS for small particles, while for larger particles with lower defect density T1 is different in static and MAS regimes and reveals elongation with increasing MAS rate. This effect is attributed to suppression of nuclear spin diffusion by MAS. We propose an approach that describes T1 dependence on the MAS rate and allows quantitative analysis of this effect.
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Size dependence of 13C nuclear spin-lattice relaxation in micro- and nanodiamonds. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:072203. [PMID: 25646270 DOI: 10.1088/0953-8984/27/7/072203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and (13)C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes. Noticeable acceleration of (13)C nuclear spin-lattice relaxation with decreasing particle size was found. We showed that this effect is caused by the contribution to relaxation coming from the surface paramagnetic centers induced by sample milling. The developed theory of the spin-lattice relaxation for such a case shows good compliance with the experiment.
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MQ NMR dynamics in dipolar ordered state at negative temperature. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2014; 61-62:49-53. [PMID: 24992818 DOI: 10.1016/j.ssnmr.2014.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 05/12/2014] [Accepted: 05/25/2014] [Indexed: 06/03/2023]
Abstract
We investigate theoretically the Multiple Quantum (MQ) NMR dynamics at negative absolute temperatures in systems of nuclear spins 1/2 coupled by the dipole-dipole interactions and with the initial conditions determined by the dipolar ordered state. Two different methods of MQ NMR are used. One of them is based on the measurement of the dipolar energy. The other method uses an additional resonance (π/4)y-pulse after the preparation period of the standard MQ NMR experiment. It is shown that at negative temperatures many-spin clusters and spin correlations are created faster, and the intensities of MQ coherences are higher than in the usual MQ NMR experiments. So, the eighth-order MQ coherence in 10-spin system of the cyclopentane molecule appears to be 1.5 times faster and its intensity is four orders higher than at positive temperatures. The proposed MQ NMR methods at negative absolute temperatures can be used for the investigation of many-spin dynamics of nuclear spins in solids.
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Antiferromagnetic Ordering of Magnetic Clusters Units in Nb(6)F(15). APPLIED MAGNETIC RESONANCE 2013; 44:143-151. [PMID: 23349566 PMCID: PMC3549236 DOI: 10.1007/s00723-012-0426-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Indexed: 06/01/2023]
Abstract
We have studied the magnetic cluster compound Nb(6)F(15) which has an odd number of 15 valence electrons per (Nb(6)F(12))(3+) cluster core, as a function of temperature using nuclear magnetic resonance, magnetic susceptibility, electron magnetic resonance and neutron powder diffraction. Nuclear magnetic resonance of the (19)F nuclei shows two lines corresponding to the apical F(a-a) nucleus, and to the inner F(i) nuclei. The temperature dependence of the signal from the F(i) nuclei reveals an antiferromagnetic ordering at T < 5 K, with a hyperfine field of ~2 mT. Magnetic susceptibility exhibits a Curie-Weiss behavior with T(N) ~5 K, and μ(eff) ~1.57 μ(B) close to the expected theoretical value for one unpaired electron (1.73 μ(B)). Electron magnetic resonance linewidth shows a transition at 5 K. Upon cooling from 10 to 1.4 K, the neutron diffraction shows a decrease in the intensity of the low-angle diffuse scattering below Q ~0.27 Å(-1). This decrease is consistent with emergence of magnetic order of large magnetic objects (clusters). This study shows that Nb(6)F(15) is paramagnetic at RT and undergoes a transition to antiferromagnetic order at 5 K. This unique antiferromagnetic ordering results from the interaction between magnetic spins delocalized over each entire (Nb(6)F(12) (i))(3+) cluster core, rather than the common magnetic ordering.
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Spin diffusion in multiple pulse spin-locking in solids containing paramagnetic impurities. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2010; 38:84-89. [PMID: 21145710 DOI: 10.1016/j.ssnmr.2010.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2010] [Revised: 11/03/2010] [Accepted: 11/08/2010] [Indexed: 05/30/2023]
Abstract
Spin diffusion and spin-lattice relaxation in solids containing paramagnetic impurities under influence of a multiple-pulse spin-locking radio-frequency sequence are studied theoretically and experimentally. The diffusion equation obtained provides a clue for determination of the time dependent magnetization. The spin-lattice relaxation time is calculated as a function of the correlation time and multiple-pulse field parameters. From the experimental data the spin diffusion coefficient, the radius of the spin diffusion barrier, and the correlation time for very slow molecular motion in polycrystalline (C(2)F)(n) system are estimated and found to be D∼7.1×10(-12)cm(2)/s, r(c)∼4.8×10(-10)m, and τ(c)∼10.2μs, respectively.
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Dynamics of multiple quantum coherences in dipole-coupling spins in solid. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2005; 28:44-9. [PMID: 15885989 DOI: 10.1016/j.ssnmr.2005.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2004] [Revised: 03/04/2005] [Accepted: 04/05/2005] [Indexed: 05/02/2023]
Abstract
A perturbation method deals with dipolar coupling spins in solids is presented. As example of application the method, the multiple-quantum coherence dynamics in clusters of a linear chain of four nuclear spins and a ring of six spins coupled by dipole-dipole interaction are considered. The calculated 0Q and 2Q intensities in a linear chain of four nuclear spins and 6Q intensity in a ring of six spins vs. the duration of the preparation period agree well with the exact solutions (for linear chain of four nuclear spins) and simulation data (for linear chain of four nuclear spins and a ring of six spin).
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Spin diffusion of dipolar energy in NQR. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2000; 16:199-202. [PMID: 10868572 DOI: 10.1016/s0926-2040(00)00082-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The theory of spin diffusion was extended to the case of nuclear dipolar order in solids containing paramagnetic impurities and nuclei with spin I > 1/2 having nuclear quadrupole moment. We show that spin diffusion process of dipolar order takes place in solids containing paramagnetic impurities. At the start of relaxation process, the direct relaxation regime is realized with non-exponential time dependence. Then the relaxation regime will be changed to diffusion-limited one. Using obtained expressions for the spin lattice relaxation times for these two relaxation regimes, the diffusion coefficient of the dipolar order in nuclear quadrupole resonance can be estimated from experimental data.
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Spin diffusion and nuclear spin-lattice relaxation in irradiated solids: a multiple-pulse NQR study. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1999; 14:145-155. [PMID: 10499660 DOI: 10.1016/s0926-2040(99)00026-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We present a detailed theoretical and experimental NQR multiple-pulse spin-locking study of spin-lattice relaxation and spin diffusion processes in the presence of paramagnetic impurities in solids. The relaxation function of the nuclear spin system at the beginning of the relaxation process is given by exp (-t/T1rho)alpha, where T1rho is spin-lattice relaxation time in rotating frame and alpha = d/6, d is the sample dimensionality. Then the relaxation proceeds asymptotically to an exponential function of time, which was attributed to the spin-diffusion regime. Using the experimental data obtained from the analysis of those two relaxation regimes in gamma-irradiated powdered NaClO3, spin diffusion coefficient has been determined and the radius of the diffusion barrier has been estimated.
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Abstract
The response of a spin system to a long (in comparison to spin-spin relaxation time T2) radiofrequency pulse has been studied. We observed that the magnetization after the long pulse does not fall to zero at time t >> T2 for both on-resonance and off-resonance conditions. The dependencies of the magnetization on frequency offset, linewidth and radiofrequency power are investigated, both theoretically and experimentally. The question of the effective field direction is also discussed.
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Nuclear spin-lattice relaxation via paramagnetic impurities in solids with arbitrary space dimension. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:10182-10187. [PMID: 9980068 DOI: 10.1103/physrevb.52.10182] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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89Y NMR and Cu NQR of hydrogenated oxygen-deficient YBa2Cu3O6.7. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:3091-3094. [PMID: 9981422 DOI: 10.1103/physrevb.52.3091] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Fractional power time dependence of the nuclear magnetization in the presence of paramagnetic impurities. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1995; 4:255-258. [PMID: 7583061 DOI: 10.1016/0926-2040(95)00004-a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We extend the theory of growth of the nuclear magnetization in the presence of paramagnetic impurities and the absence of spin diffusion to the case of multi-paramagnetic centers. We show that for short times after saturation pulses, the rate of growth of the magnetization is proportional to t alpha where t is the time and alpha = 1/3, 1/2 and 2/3 for one-, two- and three-dimensional systems, respectively. We also present experimental data for which the total time-dependent magnetization is proportional to exp[-(t/T1) alpha], which reduces to the above time dependence for short times.
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Magnetic order induced by hydrogen in superconducting RBa2Cu4O8 (R=Y,Gd) studied by Mössbauer and NQR techniques. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:15858-15863. [PMID: 9975954 DOI: 10.1103/physrevb.50.15858] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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NMR study of the 89Y resonance in fluorinated YBa2Cu3Ox. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:1290-1292. [PMID: 9975806 DOI: 10.1103/physrevb.50.1290] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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17
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Non-exponential behavior of the nuclear magnetization in H-doped copper oxides. SOLID STATE NUCLEAR MAGNETIC RESONANCE 1994; 3:23-27. [PMID: 7827975 DOI: 10.1016/0926-2040(94)90048-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Measurement of the spin lattice relaxation time in H-doped Y2BaCuO5 and YBa2Cu3O6 has revealed a power law growth of the nuclear magnetization M for short times following a saturation pulse sequence. Preliminary experimental results yield exponents of 1/2 and 1/3, depending on the amount of hydrogen present in the sample. We extend Blumberg's theory for relaxation due to paramagnetic centers via dipole-dipole interaction in the absence of spin diffusion to obtain M approximately tD/6 where D is the dimensionality of the system. This yields exponents of 1/2 and 1/3 for three- and two-dimensional systems, respectively. At long times the magnetization growth becomes exponential.
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Nuclear quadrupole resonance of Cu in hydrogenated YBa2Cu3O7. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:2821-2824. [PMID: 10006341 DOI: 10.1103/physrevb.47.2821] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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19
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NMR of 1H and 2D in hydrogen-doped and deuterium-doped YBa2Cu3O7. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:14142-14149. [PMID: 10003487 DOI: 10.1103/physrevb.46.14142] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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20
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Superconductivity and antiferromagnetism in the Cu(2) planes of YBa2Cu3O7Hx. PHYSICAL REVIEW. B, CONDENSED MATTER 1991; 43:10368-10371. [PMID: 9996757 DOI: 10.1103/physrevb.43.10368] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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21
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Influence of hydrogen on the 89Y NMR in HxYBa2Cu3O7. PHYSICAL REVIEW. B, CONDENSED MATTER 1990; 42:7949-7952. [PMID: 9994958 DOI: 10.1103/physrevb.42.7949] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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22
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1H NMR study of residual HNO3-intercalated graphite. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 39:6148-6155. [PMID: 9949040 DOI: 10.1103/physrevb.39.6148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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23
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Titanium Knight shift in titanium hydride. PHYSICAL REVIEW. B, CONDENSED MATTER 1986; 34:6917-6923. [PMID: 9939343 DOI: 10.1103/physrevb.34.6917] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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24
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Model-independent NMR approach in determining hydrogen diffusion in titanium hydride. PHYSICAL REVIEW. B, CONDENSED MATTER 1986; 33:64-67. [PMID: 9937882 DOI: 10.1103/physrevb.33.64] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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NMR study of hydrogen diffusion in zirconium hydride. PHYSICAL REVIEW. B, CONDENSED MATTER 1986; 33:68-78. [PMID: 9937883 DOI: 10.1103/physrevb.33.68] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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