SPIDER: Probing the Early Universe with a Suborbital Polarimeter

We evaluate the ability of SPIDER, a balloon-borne polarimeter, to detect a divergence-free polarization pattern ("B-modes") in the Cosmic Microwave Background (CMB). In the inflationary scenario, the amplitude of this signal is proportional to that of the primordial scalar perturbations through the tensor-to-scalar ratio r. We show that the expected level of systematic error in the SPIDER instrument is significantly below the amplitude of an interesting cosmological signal with r=0.03. We present a scanning strategy that enables us to minimize uncertainty in the reconstruction of the Stokes parameters used to characterize the CMB, while accessing a relatively wide range of angular scales. Evaluating the amplitude of the polarized Galactic emission in the SPIDER field, we conclude that the polarized emission from interstellar dust is as bright or brighter than the cosmological signal at all SPIDER frequencies (90 GHz, 150 GHz, and 280 GHz), a situation similar to that found in the "Southern Hole." We show that two ~20-day flights of the SPIDER instrument can constrain the amplitude of the B-mode signal to r<0.03 (99% CL) even when foreground contamination is taken into account. In the absence of foregrounds, the same limit can be reached after one 20-day flight.Comment: 29 pages, 8 figures, 4 tables; v2: matches published version, flight schedule updated, two typos fixed in Table 2, references and minor clarifications added, results unchange

Rhodium(ii) dimers without metal-metal bonds

Oxidation of ((Me)BDI)Rh(cyclooctene) ((Me)BDI = [2,6-Me(2)C(6)H(3)NCMe](2)CH) with Br(2) or I(2) produces paramagnetic halide-bridged Rh(II) dimers [((Me)BDI)Rh](2)(μ-X)(2) without a direct Rh-Rh bond. Steric factors are proposed to play a key role in preventing the formation of Rh-Rh bonded alternative structures

Complex long-range magnetic ordering in the Mn-bearing dugganite Pb 3TeMn3P2O14

Spin liquids, multiferroics, and doubly-chiral helical structures are just some of the exotic magnetic states found in the langasite compounds. A subclass of the langasite group, the Te6+-containing dugganites, has also shown exotic magnetism including magnetoelectric coupling, coexisting complex long-ranged ordered structures, and low-field induced magnetic transitions. Here, we present the first detailed structural study of Pb3TeMn 3P2O14 as well as the first neutron scattering measurements. This material undergoes long-range magnetic ordering, similar to the multiferroic Ba3NbFe3Si2O14, at TN=6.6 K, which is consistent with previous magnetization measurements. However unlike any other langasite or dugganite studied to date, we present evidence of a large, pseudohexagonal incommensurate supercell that alters the nuclear and magnetic structures away from the langasite ideal. \ua9 2013 Elsevier Inc.Peer reviewed: YesNRC publication: Ye

Static Magnetic Order in Tb(2)Sn(2)O(7) Revealed by Muon Spin Relaxation with Exterior Muon Implantation

Tb2Sn2O7 has been proposed as an ordered spin ice, but the precise nature of the low temperature magnetic state remains uncertain. Recent independent muon spin relaxation (mu SR) investigations suggest the possibility of exotic ground states with static order precluded on time scales longer than 10(-6) s. Here the more conventional hypothesis of canted ferromagnetism is tested by means of mu SR with the muons stopped outside the sample, as well as ultralow field bulk magnetization measurements. The field cooled state shows conventional static order, while the zero field cooled state may be interpreted in terms of conventional closed domains. These results rule out purely dynamical ground states and illustrate the value of exterior muon implantation as a complement to the conventional technique