Wednesday, October 31, 2007

Hiyam's Journal Update

Phys. Rev. B 76, 132510 (2007)
77Se NMR measurements of the -d exchange field in the organic conductor -(BETS)2FeCl4
Guoqing Wu, W. G. Clark, S. E. Brown, J. S. Brooks, A. Kobayashi, and H. Kobayashi
(Received 6 June 2007; published 26 October 2007)

77Se-NMR spectrum and frequency shift measurements in the paramagnetic metal and antiferromagnetic insulating phases are reported for a small single crystal of the organic conductor -(BETS)2FeCl4 as a function of temperature (T) and field alignment for an applied magnetic field B0=9 T. The results show that in the low T limit, where the localized Fe3+ spins (Sd=5/2) are almost fully polarized, the conduction electrons (Se electrons, spin s=1/2) in the BETS molecules experience an exchange field (Bd) from the Fe3+ spins with a value of −32.7±1.5 T at 5 K and 9 T aligned opposite to B0. This large negative value of Bd is consistent with that predicted by the resistivity measurements and supports the Jaccarino-Peter internal field-compensation mechanism being responsible for the origin of field-induced superconductivity.

Phys. Rev. B 76, 144511 (2007)
11B NMR in the layered diborides OsB2 and RuB2
B. J. Suh, X. Zong, Y. Singh, A. Niazi, and D. C. Johnston
(Received 4 June 2007; published 23 October 2007)

11B nuclear magnetic resonance (NMR) measurements have been performed on 11B enriched OsB2 and RuB2 polycrystalline powder samples in an external field of 4.7 T and in the temperature range, 4.2 K
Phys. Rev. B 76, 144405 (2007)
Multiple quantum NMR dynamics in dipolar ordered spin systems

S. I. Doronin, E. B. Fel'dman, and E. I. Kuznetsova G. B. Furman and S. D. Goren
(Received 6 December 2006; revised 28 August 2007; published 2 October 2007)

We investigate analytically and numerically the multiple-quantum (MQ) NMR dynamics in systems of nuclear spins 1/2 coupled by the dipole-dipole interactions in the case of the dipolar ordered initial state. We suggest two different methods of MQ NMR. One of them is based on the measurement of the dipolar temperature in the quasiequilibrium state which is established after the time of order (loc is the dipolar local field) after the MQ NMR experiment. The other method uses an additional resonance (/4)y pulse after the preparation period of the standard MQ NMR experiment in solids. Many-spin clusters and correlations are created faster in such experiments than in the usual MQ NMR experiments and can be used for the investigation of many-spin dynamics of nuclear spins in solids.

Phys. Rev. B 76, 144433 (2007)
NMR study of ordered states in NpFeGa5: Orbitally related ordering below 78 K
S. Kambe,H. Sakai, Y. Tokunaga, R. E. Walstedt, D. Aoki, Y. Homma, and Y. Shiokawa
(Received 18 July 2007; published 29 October 2007)

We report NMR studies on a single crystal of NpFeGa5, which has the tetragonal HoCoGa5(115) structure and exhibits two antiferromagnetically ordered states. In the antiferromagnetic I phase below 118 K, the observed internal field at the Ga(2) (4i) site is consistent with the ordered structure revealed by neutron diffraction measurements. Below 78 K in the antiferromagnetic II phase, two different Ga(2) sites with different electric field gradient tensors appear, which indicates an orbitally related ordering. A possible quadrupolar ordering in the antiferromagnetic II phase is discussed.

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