Phonon Bottleneck Effect Leads to Observation of Quantum Tunneling of the Magnetization and Butterfly Hysteresis Loops in (Et4N)3Fe2F9

A detailed investigation of the unusual dynamics of the magnetization of (Et4N)3Fe2F9 (Fe2), containing isolated [Fe2F9]3- dimers, is presented and discussed. Fe2 possesses an S=5 ground state with an energy barrier of 2.40 K due to an axial anisotropy. Poor thermal contact between sample and bath leads to a phonon bottleneck situation, giving rise to butterfly-shaped hysteresis loops below 5 K concomitant with slow decay of the magnetization for magnetic fields Hz applied along the Fe--Fe axis. The butterfly curves are reproduced using a microscopic model based on the interaction of the spins with resonant phonons. The phonon bottleneck allows for the observation of resonant quantum tunneling of the magnetization at 1.8 K, far above the blocking temperature for spin-phonon relaxation. The latter relaxation is probed by AC magnetic susceptibility experiments at various temperatures and bias fields. At H=0, no out-of-phase signal is detected, indicating that at T smaller than 1.8 K Fe2 does not behave as a single-molecule magnet. At 1 kG, relaxation is observed, occurring over the barrier of the thermally accessible S=4 first excited state that forms a combined system with the S=5 state.Comment: 10 pages, 10 figure

Second-best analysis of European energy policy : is one bird in the hand worth two in the bush?

This paper studies policy instruments that correct insufficient learning-by-doing(LbD) and research and development (R&D) of renewable electricity technologies and insufficient investments in energy efficiency (EE) in the presence of carbon pricing. The theoretical model analysis shows how to re-adjust the first-best in second-best situations, in which one of the policy instruments is restricted. Calibrated to the European power sector, the first-best choice of all instruments reduces the climate policy cost by one third. Feed-in tariffs turn out to be good substitutes for LbD, but not for R&D or EE subsidies

Butterfly Hysteresis and Slow Relaxation of the Magnetization in (Et4N)3Fe2F9: Manifestations of a Single-Molecule Magnet

(Et4N)3Fe2F9 exhibits a butterfly--shaped hysteresis below 5 K when the magnetic field is parallel to the threefold axis, in accordance with a very slow magnetization relaxation in the timescale of minutes. This is attributed to an energy barrier Delta=2.40 K resulting from the S=5 dimer ground state of [Fe2F9]^{3-} and a negative axial anisotropy. The relaxation partly occurs via thermally assisted quantum tunneling. These features of a single-molecule magnet are observable at temperatures comparable to the barrier height, due to an extremely inefficient energy exchange between the spin system and the phonons. The butterfly shape of the hysteresis arises from a phonon avalanche effect.Comment: 18 pages, 5 eps figures, latex (elsart

Moment analysis for localization in random Schrödinger operators

We study localization effects of disorder on the spectral and dynamical properties of Schrödinger operators with random potentials. The new results include exponentially decaying bounds on the transition amplitude and related projection kernels, including in the mean. These are derived through the analysis of fractional moments of the resolvent, which are finite due to the resonance-diffusing effects of the disorder. The main difficulty which has up to now prevented an extension of this method to the continuum can be traced to the lack of a uniform bound on the Lifshitz-Krein spectral shift associated with the local potential terms. The difficulty is avoided here through the use of a weak-L1 estimate concerning the boundary-value distribution of resolvents of maximally dissipative operators, combined with standard tools of relative compactness theor

Depression and Anxiety - Risk Factors in the Evolution of Breast Cancer in Women

Psychological evaluation of women with suspected or diagnosed breast cancer can provide psychooncological elements for predicting the evolution of the disease and imperative customization of specific oncological therapies. In this study, we assessed the psychological status in terms of depression, anxiety and dysfunctional attitudes in both the group of patients with a confirmed diagnosis of breast cancer and that of patients with suspected breast cancer who are in the stage of histopathological evaluation of the diagnosis. The results of the psychometric evaluations allowed the development of a common neurobiological model for the two categories of patients. Given the staging model of breast cancer, the clinical and psychometric data obtained through our study allowed us to develop an integrative neurobiological model based on the evolutionary staging of anxiety and depressive disorders (Zhao et al., 2013). Based on these hypotheses, we argue that the staging of psychological disorders, the customization of specific psychotherapeutic prophylaxis strategies and the prudent pharmacological approach to these psychological changes can significantly improve the evolution and prognosis of cancer and the quality of life of patients. The state of relative psychoemotional balance (objectified by psychometric scales), without its validation by normalizing multisystemic biological indicators of depression (C-reactive protein, proinflammatory cytokines, blood-brain barrier disruption and cerebral blood flow decrease), suggests the risk of progression of the neoplastic process. We argue that when communicating the diagnosis and the therapeutic plan, a special methodology (specific protocol) must be applied to reduce distress, correct emotional balance and improve cognitive dysfunction by supporting the motivation to survive, as well as increasing patients' self-esteem.</p