The existence of long-lived nuclear spin states in four-spin systems is explored by solution-state NMR experiments. Long-lived states are proved to exist in three different natural product molecules, each containing either a AA'BB' or a AA'XX' proton spin system. The measured state lifetimes are between four and eight times the spin-lattice relaxation time constants.

A scaling theory is applied in order to calculate the temperature dependence of the staggered magnetic susceptibility associated with the anti-ferromagnetism observed in high-temperature superconductors. In a logarithmic approximation, only a summation of the leading square logarithmic terms are taken into account, assuming the parquet approximation. We show that scaling theory can be applied t...

A method is presented to partially transfer nuclear spin polarization from one isotope S to another isotope I by the way of heteronuclear spin couplings, while minimizing the loss of spin order to other degrees of freedom. The desired I spin polarization to be detected is a design parameter, while the sequence of pulses at the two Larmor frequencies is optimized to store the greatest unused S s...

Several single-scan experiments for the measurement of the longitudinal relaxation time (T1) are proposed. These experiments result in fast and accurate determinations of the relaxation rate, are relatively robust to pulse imperfections, and preserve information about the chemical shift. The method used in these experiments is to first encode the T1 values as a spatial variation of the magnetiz...

We have performed SQUID-NMR measurements on rhodium nuclei at ultralow temperatures. With initial polarizations of up to p = 0.95, the susceptibility data showed clear indications of an antiferromagnetic tendency, but nevertheless no signs of nuclear magnetic ordering. The lowest actually measured nuclear temperature was 280 pK, whereas the lowest nuclear temperatures achieved were below 100 pK...

The transition from partial to complete spin polarization of two-dimensional electrons at half filling of the lowest Landau level has been studied using resistively detected nuclear magnetic resonance (RDNMR). The nuclear spin-lattice relaxation time is observed to be density independent in the partially polarized phase but to increase sharply at the transition to full polarization. At low temp...

The spin-lattice relaxation time τ SL is a key quantity both for the dynam-ical response of ferromagnets excited by laser pulses and as the speed limit of magneto-optical recording. Extending the theory for the electron param-agnetic resonance of magnetic impurities to spin-lattice relaxation in ferro-magnetic rare earths we calculate τ SL for Gd and find a value of 48 ps in very good agreement...

(75)As and (31)P NMR studies are performed in PrCoAsO and NdCoPO respectively. The Knight shift data in PrCoAsO indicate the presence of an antiferromagnetic interaction between the 4f moments along the c axis in the ferromagnetic state of Co 3d moments. We propose a possible spin structure in this system. The (75)As quadrupolar coupling constant, νQ, increases continuously with decrease of tem...

A model-free theoretical framework for a phenomenological description of spin-lattice relaxation by anomalous translational diffusion in inhomogeneous systems based on the fractional diffusion equation is developed. The dependence of the spin-lattice relaxation time on the size of the pores in porous glass Vycor is experimentally obtained and found to agree well with our theoretical predictions...

A model-free theoretical framework for phenomenological description of spinlattice relaxation by anomalous translational diffusion in inhomogeneous systems based on the fractional diffusion equation is developed. The dependence of the spin-lattice relaxation time on the size of the pores in porous glass Vycor is experimentally obtained and found to agree well with theoretical predictions. We ob...