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The possibility of using the transverse relaxation time T2 of protons in aqueous media for quantitative measurement of the capture of magnetic nanoparticles by cells has been studied and demonstrated. The measurement of T2 was performed on a portable original NMR relaxometer with a measuring cell for a standard well of a biological plate. The novelty of the approach is that quantitative measurements of the capture kinetics were carried out using measurements of the proton relaxation time of the nutrient medium, which is determined by the remaining number of magnetic particles (not captured by the cells) in the medium. To study the kinetics of capture, two types of magnetic nanoparticles were synthesized: magnetite particles Fe3O4 and composite particles Fe@C with an iron-carbon shell structure. The surface of the particles was functionalized with amine-and carboxyl groups. The capture of aminated particles of Fe@C cells is established by microscopy and NMR-relaxometry by measuring the time T2. It is shown that the proposed method makes it possible to register very small concentrations of trapped magnetic nanoparticles equal to tens of pg/cell.

The dependence of the transverse relaxation time T2 on the liquid, flow velocity in a porous medium (for the water and water suspension of magnetic nanoparticles (MNPs)) is studied. The T2 value allows measuring the filtration velocity of a liquid on the order of 0.05 mm/s. MNPs in a small concentration decrease T2 but at the same time the dependence of T2 on the liquid’s velocity becomes more pronounced.

This paper presents a spin modulated atomic magnetometer, different from other kinds of atomic magnetometers, the conversion coefficient between the polarization signal and the magnetic field to be measured is independent of the transverse relaxation time, which means that the higher sensitivity can be achieved when polarization is kept constant. For better understanding, the magnetic noise of spin modulated magnetometer is demonstrated and compared to SERF magnetometer. The magnetic noise measurement experiment is designed, the experimental results are consistent with the theoretical prediction. This paper validate the unique property of spin modulated magnetometer and this property will play an important role in guiding the optimization of future experiments.

A method for characterising water and oil in a rock core plug using correlations between diffusion decay in internal magnetic gradient and transverse relaxation time ( DG 0 2 - T 2 ) is presented. The method is evaluated at different saturation levels and is compared with the measurement of correlations between diffusion and transverse relaxation time ( D - T 2 ). It is shown how signals from water and oil can be separated based on their difference in diffusion decay in internal gradients. The obtained results show that the impact from heterogeneity in pore geometry and mineralogy on the individual liquids is revealed in more detail in DG 0 2 - T 2 correlations compared to the more established D - T 2 correlations. Measurements of DG 0 2 - T 2 correlations should be included in the toolbox of NMR experiments performed in the laboratory analysis of rock core plugs, and could then potentially lead to more detailed estimations of saturation levels and surface wettability properties.

Magnetic field gradients reduce the transverse relaxation time of nuclear spins, which usually degrades the sensitivity of atomic sensors based on nuclear spins. We demonstrate improved magnetic field gradient compensation by applying first-order and second-order magnetic gradients simultaneously in a cubic vapor cell containing 87Rb vapor and 129Xe gas. Compared with applying only first-order magnetic gradient compensation, the transverse relaxation time of 129Xe is up to 4.3 times longer when applying both first-order and second-order compensating magnetic gradients, which indicates that the total magnetic gradient is greatly suppressed by the joint compensation in our experiment. The magnetic gradients induced by the polarized 87Rb spins, the static magnetic field, and the residual magnetic field are also explored. As the main sources of internal magnetic inhomogeneities, these gradients are experimentally validated to have a sizable value. Furthermore, the total internal magnetic gradient in the system could be self-compensated when the directions of these internal gradient components are appropriately set. The experimental results in this paper are important for suppressing the magnetic gradients and optimizing the gradient compensation in nuclear magnetic resonance systems.

A bifunctional sensor based on Au-Fe 3 O 4 nanoparticles (NPs) modified by ethyl 1-(2-(3′,4′-dihydroxyphenyl)-2-oxoethyl)-1H-1,2,3-triazole-4-carboxylate (ETC) was developed. Due to the coordination interaction between cadmium (Cd 2+ ) and ETC, Cd 2+ induced the aggregation of Au-Fe 3 O 4 NPs from dispersion, concomitant with a change in UV–vis spectra and transverse relaxation time ( T 2 ). The combined signals provided high selectively for Cd 2+ ions.

A magnetic sensor for Cd2+ has been developed based on (Zn, Mn)-doped iron oxide nanoparticles [(Zn, Mn)Fe3O4 NPs], which was modified by ethyl 1-(2-(3′,4′-dihydroxyphenyl)-2-oxoethyl)-1H-1,2,3-triazole-4-carboxylate (ETC). ETC provided the binding sites to Cd2+ to induce the transformation of (Zn, Mn)Fe3O4 NPs from a dispersed to an aggregated state with a corresponding increase in the transverse relaxation time (T2) of surrounding water protons. Owing to the special strong interaction between ETC and Cd2+, ETC coordinated (Zn, Mn)Fe3O4 [(ETC-(Zn, Mn)Fe3O4)] NPs exhibited a low limit of detection of Cd2+ of 3.5 nM and a high selectivity over other metal ions. Furthermore, ETC-(Zn, Mn)Fe3O4 NPs can be used to detect Cd2+ in living cells by magnetic resonance (MR) imaging.

International audience; The transverse relaxation time (T2), measured with Carr-Purcell-Meiboom-Gill (CPMG) sequence, has been widely used to obtain the direct dimension data in two-dimension time domain NMR (2D TD-NMR). In this paper we are demonstrating that Continuous Wave Free Precession sequence, with low flip angle (CWFP-T1), can be an alternative to CPMG as direct detection dimension. CWFP-T1 is a fast single shot sequence, like CPMG, and yields an exponential signal governed predominantly by the longitudinal (T1) relaxation time. To obtain the correlations between T1 and T2 (T1-T2 maps) we are proposing the use of CPMG-CWFP-T1 pulse sequence. In this sequence CPMG encodes T2 information (indirect dimension) that modulates the CWFP-T1 (direct dimension) signal amplitudes. CPMG-CWFP-T1 experiments were compared with classical 2D sequences such as Saturation-Recovery-CPMG (SR-CPMG) and Inversion-Recovery-CPMG (IR-CPMG) sequence and yields similar results in phantom sample. The experimental time for the 2D sequences, using single scan, shows that SR-CPMG ' CPMG-CWFP-T1 < IR-CPMG. Experimental and simulated results demonstrated that 2D-CPMG-CWFP-T1 maps have higher resolution in T1 dimension than the techniques that uses CPMG as direct dimension. CPMG-CWFP-T1 sequence was also applied to study beef samples, and 2D maps showed higher resolution in the two fat signals than the classical IR-CPMG method. © 2019 Elsevier Inc.

The rapid prediction of fluid viscosity, especially the fluid in heavy-oil petroleum reservoirs, is of great importance for oil exploration and transportation. We suggest a new method for rapid prediction of fluid viscosity using two-dimensional (2D) NMR relaxation time distributions. DEFIR, Driven-Equilibrium Fast-Inversion Recovery, a new pulse sequence for rapid measurement of 2D relaxation times, is proposed. The 2D relation between the ratio of transverse relaxation time to longitudinal relaxation time (T1/T2) and T1 distribution of fluid are obtained by means of DEFIR with only two one-dimensional measurements. The measurement speed of DEFIR pulse sequence over 2 times as fast as that of the traditional 2D method. Using Bloembergen theory, the relation between the distributions and fluid viscosity is found. Precise method for viscosity prediction is then established. Finally, we apply this method to a down-hole NMR fluid analysis system and realized on-site and on-line prediction of viscosity for formation fluids. The results demonstrated that the new method for viscosity prediction is efficient and accurate.

The use of the effect of a decrease in the transverse relaxation time T 2 of the NMR signal of water protons in the presence of magnetic particles has been suggested for the quantitative estimation of the concentration of magnetite (Fe3O4) nanopowder in water. A calibration dependence of the relaxivity T 2 −1 on the iron concentration has been obtained for model suspensions of magnetite nanoparticles with sizes of approximately 20 nm in the concentration range of 0.15–70 mg/L. For comparison, the concentration dependences of T 2 −1 for aqueous solutions of Fe(NO3)3 · 9H2O and FeSO4 · 7H2O and paramagnetic salts Ni(NO3)2 · 9H2O, Cr(NO3)3 · 9H2O, and CuSO4 · 5H2O have been studied to show that they correlate with their paramagnetic susceptibilities.

209Bi nuclear magnetic resonance (NMR) was studied in half-Heusler compounds YPdBi and YPtBi. The observed NMR spectra exhibit low intensity because of short nuclear transverse relaxation time (T2) governed by sizable structural disorder. In both compounds, the frequency shift of the 209Bi bulk nuclei is dominated by the chemical shielding (δcs) contribution. Remarkably, it is positive for topologically trivial YPdBi yet strongly negative for topologically nontrivial YPtBi. At the same time, the spin–lattice relaxation rate (1/T1) is distinctly larger in YPtBi due to stronger spin–orbit coupling and postulated inversion of the electronic bands near the Fermi level. The unique features of δcs and 1/T1 established for YPtBi can be considered as possibly universal fingerprints of topologically nontrivial state in similar materials.

This is a study of the responses of a two-level system to a sequence of short, spatially inhomogeneous laser pulses, one of which is resonant plus one or two which are nonresonant. It is found that at certain times the system responds, and that the conditions for formation of the responses depend on the region excited by the inhomogeneously broadened line of the resonant laser pulse and the parameters of the nonresonant pulses. It is proposed that responses of this type be used for determining the transverse relaxation time of the system without delay lines for the laser pulses.

Polarized UCNs have been created by selecting only one spin state passing through a magnetized Fe foil. Typical degree of polarization was about 90 %. The polarization relaxation time in the prototype Ramsey cell was \(T_1 =1100^{+800}_{-400}\) s. Clear Ramsey resonance spectra have been observed for two precession time settings, tc = 100 ms and 30 s. The transverse relaxation time T2 was about 50 s.

In this paper we present a method to determine the pore and grain size heterogeneity using a correlation between the transverse relaxation time and the susceptibility induced inhomogeneous magnetic field. By using a CPMG echo train, we are able to correlate T 2 with the inhomogeneous internal magnetic field, B z i . We first introduce a simple simulation to study the correlation between the internal magnetic field gradient, ∣ g ∣, and B z i , where this correlation is analogous to the T 2 – B z i correlation with horizontal inversion. We then acquire experimental data from two samples, one a simple bead pack, and the other a more complicated sandstone rock core. We find that indeed this method can indicate the presence of pore and grain size heterogeneities in the sample.

the moisture distribution in untreated and esterified poplar with Maleic anhydride was studied in the present paper employed nuclear magnetic resonance (NMR). The results show that relaxation times decrease with the the fall of moisture content, and there is a linear equation between the moisture content and transverse relaxation time in esterified wood. The content of bonding water and free water in the esterified wood decreased simultaneously during the drying.

Substantial resolution and sensitivity enhancements of solid-state (1)H detected (14)N HMQC NMR spectra at very fast MAS rates up to 80 kHz, in a 1mm MAS rotor, are presented. Very fast MAS enhances the (1)H transverse relaxation time and efficiently decouples the (1)H-(14)N interactions, both effects leading to resolution enhancement. The micro-coil contributes to the sensitivity increase via strong (14)N rf fields and high sensitivity per unit volume. (1)H-(14)N HMQC 2D spectra of glycine and glycyl-L-alanine at 70 kHz MAS at 11.7 T are observed in a few minutes with a sample volume of 0.8 μL.

In this work, novel methods are suggested for assessing signal parameters of the free induction decay (FID) in nuclear magnetic resonance (NMR) experiments. The FID signal was recorded in a microtesla field and analysed to determine its relaxation time, amplitude, Larmor frequency and phase. The challenge was posed by the narrow line width, whose related effects were investigated through simulations, also. The developed methods give a new view on FID signal estimation in microtesla as well as lower and higher fields. It is shown that the transverse relaxation time of a sample can be accurately determined in the frequency domain by other means than the Lorentz peak half width. Also, with some realistic approximations, a simple functional form for the power spectrum Lorentz peak shape is proposed. As shown in this work, the inspection of the power spectrum instead of the absorption and dispersion Lorentzians is advantageous in the sense that the waveform is independent of the FID phase. The automatic and efficient methods presented in this work incorporate an integral exponential fit, the fit of the power spectrum Lorentz peak and two ways to determine the FID phase. When there are sufficiently many data points in the Lorentz peak, the power spectrum Lorentz peak shape fit provides a quick, simple and accurate way of determining the amplitude, relaxation time and Larmor frequency of the FID. In the measurements of this work, however, the narrow line width led to establishing a more applicable method which is based on the exponential decay of the Lorentz peak with a temporally moving power spectrum window.

The inversion of NMR relaxation time involves the Fredholm integral equation of the first kind. Due to its ill-posedness, numerical solutions to this type of equations are often found much less accurate and bear little resemblance to the true solution. There has been a strong interest in finding a well-posed method for this ill-posed problem since 1950s. In this paper, we prove the existence, the uniqueness, the stability and the convergence of the generalized Phillips-Twomey regularization method for solving this type of equations. Numerical simulations and core analyses arising from NMR transverse relaxation time inversion are conducted to show the effectiveness of the generalized Phillips-Twomey method. Both the simulation results and the core analyses agree well with the model and the realities.

Iron(II) carboxymethylcellulose (CMC) has been successfully employed in the synthesis of hydrophylic magnetite nanoparticles stabilized with a biopolymer coating, aiming applications in NMR imaging. The new method encompasses a convenient one-step synthetic procedure, allowing a good size control and yielding particles of about 10 nm (core size). In addition to the biocompatibility, the nanoparticles have promoted a drastic reduction in the transverse relaxation time ( T 2 ) of the water protons. The relaxivity rates have been investigated as a function of the nanoparticles concentration, showing a better performance in relation to the common NMR contrast agents available in the market.

The hyperfine fields B 0, enhancement factors η, and transverse relaxation times T 2 for 139La nuclei in La0.75Sr0.25CoO3 and La0.5Sr0.5CoO3 perovskites at 4.2 K are measured by pulsed nuclear magnetic resonance spectroscopy. The hyperfine coupling constants P for 139La nuclei in the perovskites under investigation do not depend on the composition or the crystal lattice type. The local anisotropy fields are evaluated from the data on the enhancement factor η. The dependence of the echo amplitude decay on the delay time τ of the second radio-frequency pulse does not exhibit an exponential behavior. The amplitude decay rate increases with an increase in the delay time τ. This suggests that the Suhl-Nakamura interaction contributes to the transverse relaxation time T 2.

It is shown that homogeneous broadening in induced superradiance weakly affects the cooperative exchange between forward and backward waves in a sample. At the same time, homogeneous broadening increases the delay time and attenuates the superradiance pulse intensity. As a result, it may change the regime of predominance of the transmitted or reflected wave.

The transverse relaxation time in the rotating frame T 2ρ is proposed as an effective parameter to get specific contrast in solid state imaging. Several peculiarities make T 2ρ an interesting candidate to map dynamics and structure in solids: the effect of the secular spin interaction can be controlled by the experimenter and therefore the relaxation associated with the nonsecular terms, which is particularly sensitive to very slow dynamics, can be observed. In this paper we present preliminary results obtained on polymers and prove the capability of the MARF Imaging, enhanced by a filter based on rotary echo refocusing, to produce images of solids contrasted by T 2ρ .

Radiation damping effects on the determination of transverse relaxation times are discussed. Precise measurements in the presence of radiation damping are suggested. In the strong radiation damping case, the spin-spin relaxation time T 2 could not be measured by the simple spin-echo technique, but can be determined by an exponential fitting of the CPMG echo amplitudes while the effective transverse relaxation time T 2 * can be determined by extrapolating the line widths in a saturation-recovery experiment to an infinitely short recovery time.

NMR water proton transverse relaxation time distributions are shown to provide valuable information about the distribution of ice and nonfreezing water in complex heterogeneous systems. In a model system consisting of randomly packed Sephadex beads the NMR data confirm that ice inside the porous Sephadex beads coexists as a two phase system with unfrozen dextran gel. The NMR relaxation technique is shown to provide complementary information to both differential scanning calorimetry and cryomicroscopy.

Among the different fields of research in nuclear magnetic resonance (NMR) which are currently investigated in the Laboratory of Biomolecular Magnetic Resonance (LRMB), two subjects that are closely related to each other are presented in this article. On the one hand, we show how to populate long-lived states (LLS) that have long lifetimes TLLS which allow one to go beyond the usual limits imposed by the longitudinal relaxation time T1. This makes it possible to extend NMR experiments to longer time-scales. As an application, we demonstrate the extension of the timescale of diffusion measurements by NMR spectroscopy. On the other hand, we review our work on long-lived coherences (LLC), a particular type of coherence between two spin states that oscillates with the frequency of the scalar coupling constant JIS and decays with a time constant TLLC. Again, this time constant TLLC can be much longer than the transverse relaxation time T2. By extending the coherence lifetimes, we can narrow the linewidths to an unprecedented extent. J-couplings and residual dipolar couplings (RDCs) in weakly-oriented phases can be measured with the highest precision.

SQUID-based MRI (magnetic resonance imaging) at microtesla fields has developed significantly over the past few years. Here we describe application of this method for magnetic relaxation measurements in the living human brain. We report values of the longitudinal relaxation time T1 for brain tissues, measured in vivo for the first time at microtesla fields. The experiments were performed at 46 microtesla field using a seven-channel SQUID system designed for microtesla MRI and MEG. Values of T1, measured for different tissues at this field, are found to be close (within 5%) to the corresponding values of the transverse relaxation time T2 at the same field. Implications of this result for imaging contrast in microtesla MRI are discussed., To appear in Proceedings of 2008 Applied Superconductivity Conference

Measurements of the transverse relaxation time T2 are usually conducted with the Carr Purcell Meiboom Gill (CPMG) pulse sequence, which causes T2-weighted magnetization. Diffusion effects are a common source of error in measurements of this kind, because the incoherent motion of spins in external magnetic field gradients distorts T2 weighting of the transverse magnetization. As a result, inaccurate T2-values are obtained. In this work, we present a method which completely compensates for the effect of diffusion.

The interface structure of [Cu/Co/Cu/NiFe] superlattices, in which the giant magnetoresistance is induced by a small external field, has been investigated by 59Co nuclear magnetic resonance in zero field. A very broad line ranging from 100 to 230 MHz was observed. The frequency dependence of the transverse relaxation time T2 and the enhancement factors η is discussed.

In this paper chemometrics (ANOVA and PCR) is used to measure unbiased correlations between NMR spin-echo decays of pork M. Longissimus dorsi obtained through Carr–Purcell–Meiboom–Gill (CPMG) experiments at low frequency (20 MHz) and the values of 14 technological parameters commonly used to assess pork meat quality. On the basis of the ANOVA results, it is also found that the CPMG decays of meat cannot be best interpreted with a “discrete” model (i.e., by expanding the decays in a series of a discrete number of exponential components, each with a different transverse relaxation time), but rather with a “continuous” model, by which a continuous distribution of T 2 's is allowed. The latter model also agrees with literature histological results.

A new technique of measuring extremely short electron spin-lattice relaxation times T1∼10−6–10−10 sec is developed and applied to study some oxide high-Tc materials, related compounds and fullerides RbC60.

The changes in water proton transverse relaxation behaviour induced by aggregation of Bovine serum albumin are explained in terms of the simple molecular processes of diffusion and chemical exchange without recourse to invoking changes in ‘bound’ water or the ‘state’ of water in the system. It is proposed that the main effect of aggregation is to reduce the protein proton transverse relaxation time because dipole-dipole interactions between protein protons are no longer as efficiently averaged by rotational motions, this in turn causes a reduction in water proton transverse relaxation time since water protons are in fast chemical exchange with protein protons. Diffusive exchange between water molecules then spatially averages the water proton signal to an extent that depends on the morphology of the aggregate-water system. The diffusive averaging process can give rise to multi-exponential relaxation.

Experimental observation of ultrasonic free induction decay in glasses at low temperatures is presented. The variations of the decay time as a function of the input power have been observed and measured. The data are interpreted in the framework of the two-level systems (TLS) theory and we show that such an experiment provides us with a simple measurement of the transverse relaxation time T 2 of the TLS.

In a recent paper, Tenti and McCourt [J. Chem. Phys. 65, 623 (1976)] presented theoretical evidence for the existence of a minimum in the transverse relaxation time T2 of the nuclear magnetization in dilute gases. Here the transverse relaxation rate is reexamined and it is shown that in the low density regime it is impossible to define a T2. Moreover, the slowing down of the relaxation rate at low densities is due to a decreasing collision rate and not to a dynamical shift as reported by Tenti and McCourt. It is found that the transverse magnetization behaves as a damped oscillator below a certain critical density. Explicit calculations are presented for H2 gas and for this system the T2 description breaks down below 0.02 Torr.

The measure of transverse relaxation time T2 of 7Li permits precise study of the diffusion of the nucleus, which has already been observed by 119Sn Mossbauer spectroscopy in three phosphides. The analysis of Hendrickson and Bray has been applied to the results obtained as a function of temperature. A discontinuity in the processes of diffusion is observed, and a possible explanation has been proposed.

Transient behavior of optical bistable system is studied theoretically for switching from the high light-transmitting state to the low one. For three-level system in solids, e.g., the ground, the exciton and the bi-exciton states in CuCl, the optical bistability is shown to be possible and to respond in the transverse relaxation time of an order of pico-second by adjusting the degree of the off-resonance of the incident field as well as the detuning of the Fabry-Perot cavity. Thus we will be able to dissolve the largest obstacle to application of the optical bistability to an optical device.

A nonlinear optical method to determine the transverse relaxation time of excitonic molecules by means of two-photon echo is proposed. In the case of two-photon transition such as excitonic molecule one needs three pulses to obtain an echo signal. When the wave-vector and frequency of the three successive pulses are denoted by k 1 ,ω 1 , k 2 ,ω 2 and k 3 ,ω 3 , the two-photon echo can be observed in the direction of 4k 2 -2k 1 -k 3 with frequency 4ω 2 -2ω 1 -ω 3 . Tuning both ω 1 and ω 2 to be two-photon resonant with excitonic molecule, we can satisfy the phase-matching condition rather easily for appropriate values of ω 3 due to the large dispersion of excitonic polaritons. From the correlation trace of the two-photon echo we can determine directly the transverse relaxation time of excitonic molecules.

The effect of radio frequency inhomogeneities on nuclear magnetic transverse relaxation time (T2) measurements has been investigated experimentally and numerically. Measurements using the Meiboom‐Gill modification to the Carr‐Purcell sequence have been emphasized; however, some other methods have been considered. The calculations have been performed assuming that the magnetization obeys (a) the Bloch equations and (b) the modified Bloch equations. In case (a) the errors resulting from rf field inhomogeneities were found to be small to moderate, and a method is presented whereby the upper limits to these errors can be determined experimentally. Furthermore, the errors are decreased considerably in a homogeneous main magnetic field adjusted to resonance and go to zero when T1 = T2. In case (b) the errors were considerably larger than in case (a) and the presence of a homogeneous main magnetic field did not necessarily decrease these errors. Even quite small rf field inhomogeneities were found to produce sig...

For liquid methanol, the longitudinal relaxation of the OH and CH3 proton magnetic moments was found to depend on the rate of OH proton exchange between methanol molecules. This exchange dependence is explained quantiatively in terms of cross relaxation between the OH and CH3 protons resulting from the scalar interaction J(t)I·S. The good agreement obtained between experiment and theory indicates that measurement of the longitudinal relaxation rate can be used to obtain accurate values for the rate of proton exchange in methanol. In addition, for the range of rates where the longitudinal relaxation is affected, the spin—echo determination of T2, the transverse relaxation time, was found to be reliable for the CH3 proton but not for the OH proton.

Knight shift and some other properties of Cu nuclear magnetic resonance in Cu-Pd alloys were measured. It was observed that the shift is negative, and its magnitude is almost proportional to the susceptibility, having the value of -0.9% at 1 atomic percent of Cu. A deviation from the proportionality was observed in Cu dilute region and it is suggested that the charge screening radius is of short range. The transverse relaxation time increases with the concentration of Pd, and the resonance line width takes a maximum value at 25% Pd. The longitudinal relaxation time keeps a constant value, about 1/3 of that of pure Cu metal, through all the concentration measured.

Atomic relaxation in the presence of a strong coherent optical field is examined. Contrary to popular practice, we find that the Bloch equations do not apply when the applied field is strong enough to saturate the transition. The component of the induced polarization in phase with the field lives longer than the out-of-phase component. One important consequence is that pulse durations for adiabatic inversion of atomic levels need not be short relative to the transverse relaxation time of the atom if the pulse amplitude is sufficiently large.

Temperature dependence of the transverse relaxation time T2 of Fe57 NMR signal in DyFe0.008 Co0.002 O3 is investigated both theoretically and experimentally in the vicinity cf the first order Morin-type phase transition. Anomalous increase of the relaxation time at approaching the Morin point is shown to be due to dynamic coupling between the electronic and nuclear spin subsystems.

Spin echo NMR and ac susceptibility measurements have been performed at 60 mK∼4.2 K in (Ce 1- x Gd x )Ru 2 . The sharp superconducting transition is confirmed for x ≦0.110. The NMR signals associated with the ferromagnetically ordered Gd atoms are observed down to x =0.105 in zero external field and to x =0.095 with applying field. The hyperfine field at Gd site changes as -206+88· x kOe. The intensity of the signal in zero field decreased rapidly in accordance with the appearance of superconductivity. The temperature, concentration and external field dependence of the transverse relaxation time T 2 show that T 1 is governed mainly by the Weger mechanism. The rapid increase of T 1 with lowering temperature for 0.105≦ x ≦0.110 indicates a possible appearance of small energy gap associated with superconducting state. The results support the coexistence of superconductivity and ferromagnetism.

We report solutions for the paramagnetic magnetization of a two-level spin system for terms varying at the second-harmonic frequency of the driving field and their use to determine the power dependence of the transverse relaxation time T 2 in saturated spin systems.

NMR on 3He atoms in the very small pores of Vycor glass reveals magnetic states which are temperature, pressure, and magnetic field dependent. The susceptibility is Curie-Weiss-like with a Θ that increases with pressure. The longitudinal relaxation time τ1 is a weak, monotonically increasing function of temperature. The transverse relaxation time τ2 is a strong function of temperature at low temperature, with a positive slope at 286 gauss and a negative slope at 71.5 gauss.