Spin polarization contrast observed in GaAs by force-detected nuclear magnetic resonance

We applied the recently developed technique of force-detected nuclear magnetic resonance (NMR) to observe 71Ga, 69Ga, and 75As in GaAs. The nuclear spin-lattice relaxation time is 21$\pm$5 min for 69Ga at $\sim 5$ K and 4.6 Tesla. We have exploited this long relaxation time to first create and then observe spatially varying nuclear spin polarization within the sample, demonstrating a new form of contrast for magnetic resonance force microscopy (MRFM). Such nuclear spin contrast could be used to indirectly image electron spin polarization in GaAs-based spintronic devices.Comment: 3 pages, 2 figure

Study of the Solid State Properties of an Organic Superconductor

ABSTRACTWe have synthesized cooper(I)di[bis(ethylenedithiolo)terathiafulvalene] bis(isothiocyanato), [(BEDT-TTF)2]+[Cu(NCS)2]using standard electrochemical methods. Single crystal samples of the compound were obtained and were found to have superconducting transition temperatures of 10.4 K, using DC conductivity measurements. [(BEDT-TTF)2+[Cu(NCS)2] shows a region between room temperature and 90 K which appears to be“semiconducting”To characterize the structure of the samples we used Scanning Tunneling Microscopy (STM). STM supplied real-space images of the sample surface in accordance to its electronic structure. Ravy observed diffuse streaks between Bragg spots in his X-ray data of [(BEDT-TTF)2+[Cu(NCS)2]−, which he attributes to a stacking fault at every fourth repetition of the anion in the crystal structure [1]. STM shows no evidence for such disorder in [−(BEDT-TTF)2]+[Cu(NCS)2]−of the type proposed, and in fact illustrates direct evidence to the contrary. An intensity modulation in the STM data supports the possibility of a charge density wave commensurate with the lattice. This interpretation is consistent with the calculated Fermi surface which allows nesting of the wave vector and may explain the peculiar behavior of the temperature dependency of the conductivity data in the normal region.</jats:p