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Investigations of the spin dynamics of the geometrically frustrated pyrochlore (Tb(p)Y(1-p))2Ti2O7, using muon spin relaxation and neutron spin echo, as a function of magnetic coverage p, have been carried out. Our major finding is that paramagnetic fluctuations prevail as T-->0 for all values of p, and that they are sensitive to dilution, indicating a cooperative spin motion. However, the percolation threshold pc is not a critical point for the fluctuations. We also find that the low temperature spectral density has a 1/f behavior, and that dilution slows down the spin fluctuations.

Muon spin relaxation and magnetic susceptibility measurements have been performed on the pure and diluted spin 1/2 kagomé system (CuxZn(1-x))3V2O7(OH)2 2H2O. In the pure x=1 system we found a slowing down of Cu spin fluctuations with decreasing temperature towards T approximately 1 K, followed by slow and nearly temperature-independent spin fluctuations persisting down to T=50 mK, indicative of quantum fluctuations. No indication of static spin freezing was detected in either of the pure (x=1.0) or diluted samples. The observed magnitude of fluctuating fields indicates that the slow spin fluctuations represent an intrinsic property of kagomé network rather than impurity spins.

We report muon spin relaxation (µSR) and magnetization measurements, together with synthesis and characterization, of the Li-intercalated layered superconductors Li x HfNCl and Li x ZrNCl with/without co-intercalation of THF

Muon spin relaxation (µSR) measurements in high transverse magnetic fields ( ĉ) revealed strong field-induced quasi-static magnetism in the underdoped and Eu doped (La,Sr)2CuO4 and La1.875Ba0.125CuO4, existing well above Tc and TN . The susceptibility-counterpart of Cu spin polarization, derived from the muon spin relaxation rate, exhibits a divergent behavior towards T ∼ 25 K. No field-induced magnetism was detected in overdoped La1.81Sr0.19CuO4, optimally doped Bi2212, and Zn-doped YBa2Cu3O7.

A series of pyrene derivatives containing thienyl groups, 1−3, has been prepared using the Suzuki coupling reaction. Recrystallization from solution and physical vapor transport (PVT) method afforded different types of crystals of 1. From the mixture of isomers of 2, the 1,8-isomer preferably crystallized from solution, whereas the 1,6-isomer crystal was obtained by the PVT method. Fabricating single-crystal-based field-effect transistors of the above compounds we directly compared the field-effect performance between the devices of the two isoforms of 1 and those of the two isomers of 2. Though the overlap integrals were calculated to be only ∼10−3, the best hole mobility reached 0.02 cm2 V−1 s−1 for one of the single crystals of 1. Intriguingly, for both 1 and 2 only one type of the crystal shows the field-effect characteristics, indicating the significance of molecular packing even in the absence of band transport among the poorly coupled molecules. The estimated intermolecular overlap integrals for each compound also imply that the minimum overlap integral of ∼10−2 eV is required for detection of the field-effect characteristics.

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Muon spin rotation/relaxation measurements have been performed in the itinerant helical magnet MnSi at ambient pressure and at 8.3 kbar. We have found the following: (a) the spin-lattice relaxation rate 1/T(1) shows divergence as T1T proportional, variant (T-T(c))(beta) with the power beta larger than 1 near T(c); (b) 1/T(1) is strongly reduced in an applied external field B(L) and the divergent behavior near T(c) is completely suppressed at B(L)> or =4000 G. We discuss that (a) is consistent with the self-consistent renormalization theory and reflects a departure from "mean-field" behavior, while (b) indicates selective suppression of spin fluctuations of the q=0 component by B(L).