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Using X-band pulsed electron spin resonance, we report the intrinsic spin-lattice (T1) and phase coherence (T2) relaxation times in molecular nanomagnets for the first time. In Cr7M heterometallic wheels, with M = Ni and Mn, phase coherence relaxation is dominated by the coupling of the electron spin to protons within the molecule. In deuterated samples T2 reaches 3 µs at low temperatures, which is several orders of magnitude longer than the duration of spin manipulations, satisfying a prerequisite for the deployment of molecular nanomagnets in quantum information applications.Certain computational tasks can be efficiently implemented using quantum logic, in which the informationcarrying elements are permitted to exist in quantum superpositions [1]. To achieve this in practice, a physical system that is suitable for embodying quantum bits (qubits) must be identified. Some proposed scenarios employ electron spins in the solid state, for example phosphorous donors in silicon [2], quantum dots [3], heterostructures [4] and endohedral fullerenes [5,6], motivated by the long electron-spin relaxation times exhibited by these systems. An alternative electron-spin based proposal exploits the large number of quantum states and the non-degenerate transitions available in high spin molecular magnets [7,8]. Although these advantages have stimulated vigorous research in molecular magnets [9,10,11], the key question of whether the intrinsic spin relaxation times are long enough has hitherto remained unaddressed. Here we show, using pulsed electron spin resonance experiments on heterometallic wheels, that the relaxation times in molecular magnets can significantly exceed the duration of coherent manipulations, a prerequisite for the deployment of these systems in quantum information applications.Molecular magnets comprising clusters of exchanged coupled transition metal ions have been studied extensively in recent years [12]. They can exhibit a substantial ground state spin with a large and negative zerofield splitting (ZFS), leading to a spontaneous magnetic moment parallel to the easy axis. In the absence of a magnetic field, the configurations in which the moment is 'up' or 'down' relative to the easy axis are degenerate, and this bistable nature has stimulated interest in the application of magnetic clusters as classical [13] or quantum [7,8,9, 11] information elements.Molecules in this class have been synthesised with widely varying properties, from the S = 10 highly axial Mn 12 -acetate [14], to the diamagnetic ring Cr 8 F 8 Piv 16 [15,16]. A key recent chemical advance is the the development of procedures for magnetically 'doping' a diamagnetic cluster to synthesise paramagnetic molecules in a systematic and controllable way [17]. Thus, substituting a Cr 3+ (s = 3/2) by a Mn 2+ (s = 5/2) or a Ni 2+ (s = 1) generates the S = 1 Cr 7 Mn or the S = 1/2 Cr 7 Ni respectively.Many clusters have been investigated using thermodynamic probes such as magnetization [18] and heat capacity [19], and spectroscopic probes such as neutr...

The tetragonal phase of Fe 1+ Se (0.01 ≤  ≤ 0.04) with the anti-PbO-type crystal structure displays superconductivity (T c ~ 8.5 K) when  = 0.01 and the superconductivity is destroyed by additional interstitial Fe. 9 The compound bears close structural resemblance to LiFeAs 10 (both compounds contain FeQ 4 (Q = Se, As) tetrahedra that are highly compressed in the basal plane compared with other iron-based superconductors) and both compounds differ from the canonical iron-based superconducting system in that they superconduct when as close to stoichiometric as possible (i. The lithium/ammonia solutions were rapidly decolourised by Fe 1+ Se at -78 °C. This is consistent either with the classic method for decomposing the metastable solution of solvated electrons using a "rusty nail" as a catalyst for the formation of lithium amide and hydrogen, or it indicates. Donation of the solvated electrons from the alkali metal ammonia solution to empty bands in the solid with Li ions co-inserted to balance the charge in a reductive intercalation reaction. The product was a black powder with a much finer grain size than the parent Fe 1+ Se material. The products were extremely air sensitive. X-ray powder diffraction (XRPD) showed no evidence for the starting material or other products above the 5% level and the diffraction peaks were indexed on a body centred tetragonal unit cell with lattice parameters a = 3.8249(2) Å and c = 16.5266(9) Å at room temperature. The basal lattice parameter, a (= √2 × Fe-Fe distance) is 1.4% larger than the value of 3.7734(1) Å reported for Fe 1.01 Se. 9 The c lattice parameter of 16.5266 (9) Neutron powder diffraction (NPD) patterns were collected from samples synthesised using 0.5 moles of Li per mole of FeSe with either NH 3 or ND 3 as solvent. The XRPD patterns of these products were similar, but their NPD patterns were dramatically different (the intensities varied greatly between the two compounds because of the greatly different neutron scattering lengths for H (-3.74 fm) and D (+6.67 fm), and the H-containing material produced a characteristic incoherent background) proving that the samples contain H(D). A structural model was obtained from the deuterated sample by starting from the model suggested by the X-ray refinements with N in the site 8-coordinate by Se and computing Fourier difference maps to reveal the remaining nuclear scattering density. Refinements against data from the GEM diffractometer at room temperature and the HRPD diffractometer at 8 K on the same sample of deuterated material produced similar structural models at the two temperatures. The initial assumption of a formula (LiND 2 )Fe 2 Se 2 resulted in an apparently satisfactory fit to the low temperature HRPD data (which emphasises the short d-spacing data) using a model in which the D atoms were located on crystallographic positions (16m site: (x, x, z)) which refined freely to be about 1 Å from the N atom (2a site: (0, 0, 0)) and with the N-D bonds directed towards the selenide anions. In this initial model the...

A positive muon is a spin-1/2 particle. Beams

An understanding of thermal physics is crucial to much of modern physics, chemistry, and engineering. This book provides a modern introduction to the main principles that are foundational to thermal physics, thermodynamics, and statistical mechanics. The key concepts are carefully presented in a clear way, and new ideas are illustrated with worked examples as well as a description of the historical background to their discovery. Applications are presented to subjects as diverse as stellar astrophysics, information and communication theory, condensed matter physics, and climate change. Each chapter concludes with detailed exercises. This second edition of the text maintains the structure and style of the first edition but extends its coverage of thermodynamics and statistical mechanics to include several new topics, including osmosis, diffusion problems, Bayes theorem, radiative transfer, the Ising model, and Monte Carlo methods. New examples and exercises have been added throughout.