The discovery and renaissance of dynamic nuclear polarization.

In 1952, Overhauser proposed a method for transferring the large electron spin polarization of conduction electrons in a metal to the metal nuclei, enhancing their polarization one thousand fold. Such an enhancement method is called dynamic nuclear polarization (DNP). The article explains his idea, describes the experiments of Carver and Slichter that confirmed his proposal, their demonstration that the method was not limited to metals, describes the nature of immediate impact on the magnetic resonance community, discusses why DNP was not broadly utilized for many years, explains in simple terms how the method works and reports on the new developments in experimental methods that have given DNP an active and exciting future.

The discovery and demonstration of dynamic nuclear polarization--a personal and historical account.

The paper gives some background about prewar studies of paramagnetic relaxation, the author's postwar measurements of paramagnetic relaxation using 3 cm microwaves, the beginning studies of alkali metal NMR at Illinois, Overhauser's arrival and proposal, the discovery of the ESR of conduction electrons, the experiment confirming his idea in Li and Na metals, then in solutions of Na atoms in liquid ammonia, and the realization that a form of Overhauser effect might be seen when several isotopes were present in cases where atoms were mobile. Two other experiments at Illinois inspired by the Overhauser experiments are briefly described: measurement of the spin susceptibility of conduction electrons and measurement of spin-lattice relaxation times in superconductors.

Evidence for two electronic components in high-temperature superconductivity from NMR.

A new analysis of (63)Cu and (17)O NMR shift data on La(1.85)Sr(0.15)CuO(4) is reported that supports earlier work arguing for a two-component description of La(1.

Precise determination of the orientation of the Dzialoshinskii-Moriya vector in kappa-(BEDT-TTF)2Cu[N(CN)(2)]Cl.

A novel electron spin-reorientation transition is discovered by 13C NMR in the quasi-two-dimensional organic antiferromagnet kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl. The spin reorientation occurs as an external field is swept through the orientation of the characteristic vector of the Dzialoshinskii-Moriya (DM) interaction, thus providing a precise determination of the orientation of the DM vector. Such a spin reorientation could help to characterize the DM interaction in other antiferromagnetic systems.

Double resonance probes for close frequencies.

A new double resonance probe design for NMR experiments for systems with close resonance frequencies is introduced. The design is based on two coupled resonators and was extensively tested on magnetically aligned powders of several high temperature superconductors by performing double resonance experiments between the 65Cu and 63Cu isotopes as well as between transitions of different magnetic quantum number of the same spin. The probe's performance approaches that of a single resonance circuit and it has only 4 variable tuning/matching elements.

Contributions of spin-lattice relaxation to the echo decay of planar Cu in high-temperature superconductors.

Measurement of T2G, the Gaussian component of the spin-echo envelope of planar Cu nuclei in high-temperature superconductors, gives important information about the real part of the Cu electron spin susceptibility. In the traditional picture of the planar Cu echo decay, the internuclear coupling is assumed to remain static with respect to spin-lattice relaxation and mutual exchange fluctuations. In some circumstances, however, this assumption breaks down.