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Current scientific consensus holds that sound is transmitted, solely mechanically, from the tympanum to the cochlea via ossicles. However this theory does not explain the hearing extreme quality regarding high frequencies in mammals. So, we propose a bioelectronic pathway (the covert path) that is complementary to the overt path. We demonstrate experimentally that the tympanum produces piezoelectric potentials isochronous to acoustic vibrations thanks to its collagen fibers and that their amplitude increases along with the frequency and level of the vibrations. This finding supports the existence of an electrical pathway, specialized in transmitting high-frequency sounds that works in unison with the mechanical pathway. A bio-organic triode, similar to a field effect transistor, is the key mechanism of our hypothesized pathway. We present evidence that any deficiency along this pathway produces hearing impairment. By augmenting the classical theory of sound transmission, our discovery offers new perspectives for research into both normal and pathological audition and may contribute to an understanding of genetic and physiological problems of hearing.

The chromium(II) orthophosphate {\alpha}-Cr3(PO4)2 is a weak ferrimagnet with the Curie temperature TC = 29 K confirmed by a \lambda-type peak in specific heat. Dominant antiferromagnetic interactions in this system are characterized by the Weiss temperature {\Theta} = - 96 K, indicating an intermediate frustration ratio |{\Theta}|/TC ~ 3. In its magnetically ordered states {\alpha}-Cr3(PO4)2 exhibits a remarkable sequence of temperature-induced magnetization reversals sensitive to the protocol of measurements, i.e. either field-cooled or zero-field-cooled regimes. The reduction of the effective magnetic moment 4.5 {\mu}B/Cr2+, as compared to the spin-only moment 4.9 {\mu}B/Cr2+, cannot be ascribed to the occurence of the low-spin state in any crystallographic site of the Jahn-Teller active 3d4 Cr2+ ions. X-ray absorption spectra at the K-edge indicate divalent chromium and unravel the high-spin state of these ions at the L2,3-edges. Weak ferrimagnetism and multiple magnetization reversal phenomena seen in this compound could be ascribed to incomplete cancellation and distortion of partial spontaneous magnetization functions of Cr2+ in its six crystallographically inequivalent positions., Comment: 17 pages, 9 figures

We report on magneto-transport measurement in disordered graphene under pulsed magnetic field of up to 57T. For large electron or hole doping, the system displays the expected anomalous Integer Quantum Hall Effect (IQHE) specific to graphene up to filling factor $\nu=2$. In the close vicinity of the charge neutrality point, the system breaks up into co-existing puddles of holes and electrons, leading to a vanishing Hall and finite longitudinal resistance with no hint of divergence at very high magnetic field. Large resistance fluctuations are observed near the Dirac point. They are interpreted as the the natural consequence of the presence of electron and hole puddles. The magnetic field at which the amplitude of the fluctuations are the largest is directly linked to the mean size of the puddles.

We report a detailed examination the magnetic structure of anhydrous cupric chloride CuCl2 carried out by powder neutron diffraction, magnetic susceptibility and specific heat measurements on polycrystalline and single crystal samples as well as an evaluation of the spin exchange interactions by first principles density functional theory (DFT) calculations. Anhydrous CuCl2 shows one dimensional antiferromagnetic behavior and long range antiferromagnetic ordering below a Neel temperature of 23.9 K. Neutron powder and single crystal diffraction reveal that, below 23.9K, CuCl2 undergoes a phase transition into an incommensurate magnetic structure (propagation vector (1,0.2257,0.5) with a spin-spiral propagating along b and the moments confined in the bc crystallographic plane. Our DFT calculations show that the spin-spiral results from competing ferromagnetic nearest neighbor and antiferromagnetic next-nearest neighbor spin-exchange interaction along the spin chains. Implications for possible multiferroic behavior of CuCl2 are discussed., Comment: 40 pages, 20 Figures

The weak itinerant ferromagnet UIr is studied by magnetization and magnetostriction measurements. Critical behavior, which surprisingly extends up to several Tesla, is observed at the Curie temperature $T_C\simeq45$ K and is analyzed using Arrott and Maxwell relations. Critical exponents are found that do not match with any of the well-known universality classes. The low-temperature magnetization $M_s\simeq0.5$ $\mu_B \cong const.$ below 3 T rises towards higher fields and converges asymptotically around 50 T with the magnetization at $T_C$. From the magnetostriction and magnetization data, we extract the uniaxial pressure dependences of $T_C$, using a new method presented here, and of $M_s$. These results should serve as a basis for understanding spin fluctuations in anisotropic itinerant ferromagnets., Comment: 4 pages, 3 figures

We have investigated the dimensionality and origin of the magnetotransport properties of LaAlO3 films epitaxially grown on TiO2-terminated SrTiO3(001) substrates. High mobility conduction is observed at low deposition oxygen pressures (PO2 < 10^-5 mbar) and has a three-dimensional character. However, at higher PO2 the conduction is dramatically suppressed and nonmetallic behavior appears. Experimental data strongly support an interpretation of these properties based on the creation of oxygen vacancies in the SrTiO3 substrates during the growth of the LaAlO3 layer. When grown on SrTiO3 substrates at low PO2, other oxides generate the same high mobility as LaAlO3 films. This opens interesting prospects for all-oxide electronics., Comment: 4 pages, 4 figures. Accepted for publication in Phys. Rev. Lett

We present the results of a crystal structure determination using neutron powder diffraction as well as the superconducting properties of the rare-earth sesquicarbide La2C3 (Tc ~ 13.4 K) by means of specific heat and upper critical field measurements. From the detailed analysis of the specific heat and a comparison with ab-initio electronic structure calculations, a quantitative estimate of the electron-phonon coupling strength and the logarithmic average phonon frequency is made. The electron-phonon coupling constant is determined to \lambda ~ 1.35. The electron-phonon coupling to low energy phonon modes is found to be the leading mechanism for the superconductivity. Our results suggest that La2C3 is in the strong coupling regime, and the relevant phonon modes are La-related rather than C-C stretching modes. The upper critical field shows a clear enhancement with respect to the Werthamer-Helfand-Hohenberg prediction, consistent with strong electron-phonon coupling. Possible effects on the superconducting properties due to the noncentrosymmetry of the crystal structure are discussed., Comment: 12 pages, 11 figures, submitted to Phys. Rev. B

In this paper we demonstrate the application of high magnetic fields to study the magnetic properties of low dimensional spin systems. We present a case study on the series of 2-leg spin-ladder compounds Na$_2$T$_2$(C$_2$O$_4$)$_3$(H$_2$O)$_2$ with T = Ni, Co, Fe and Mn. In all compounds the transition metal is in the $T^{2+}$ high spin configuation. The localized spin varies from S=1 to 3/2, 2 and 5/2 within this series. The magnetic properties were examined experimentally by magnetic susceptibility, pulsed high field magnetization and specific heat measurements. The data are analysed using a spin hamiltonian description. Although the transition metal ions form structurally a 2-leg ladder, an isolated dimer model consistently describes the observations very well. This behaviour can be understood in terms of the different coordination and superexchange angles of the oxalate ligands along the rungs and legs of the 2-leg spin ladder. All compounds exhibit magnetic field driven ground state changes which at very low temperatures lead to a multistep behaviour in the magnetization curves. In the Co and Fe compounds a strong axial anisotropy induced by the orbital magnetism leads to a nearly degenerate ground state and a strongly reduced critical field. We find a monotonous decrease of the intradimer magnetic exchange if the spin quantum number is increased.

We consider the spin-1/2 antiferromagnetic Heisenberg chain in a staggered magnetic field describing materials such as copper benzoate and copper pyrimidine dinitrate. Using the density-matrix renormalization group for transfer matrices (TMRG) we calculate the magnetization of these materials at finite temperature and arbitrary magnetic field. These results are in excellent agreement with experimental data, allowing for a determination of the inhomogeneity parameter c of copper benzoate (c = 0.043) and copper pyrimidine dinitrate (c= 0.11). The TMRG approach can be applied to rather low temperatures yielding singular field and temperature dependences of susceptibilities., Comment: 4 pages, 5 figures

We have investigated the high field magnetisation of the frustrated one dimensional compound LiCuVO4. In zero field, LiCuVO4 undergoes long range antiferromagnetic order at T_{N} ~ 2.5 K with a broad short range Schottky type anomaly due to one dimensional correlations in the specific heat at 32 K. Application of a magnetic field induces a rich phase diagram. An anomaly in the derivative of the magnetisation with respect to the applied magnetic field is seen at ~ 7.5 T with H ll c in the long range order phase. We investigated this in terms of a first experimental evidence of a middle field cusp singularity (MFCS). Our numerical DMRG results show that in the parameter range of LiCuVO4 as deduced by inelastic neutron scattering (INS), there exists no MFCS. The anomaly in the derivative of the magnetisation at ~ 7.5 T is therfore assigned to a change in the spin structure from the ab plane helix seen in zero field neutron diffraction., Comment: 7 pages, 4 figures, to appear as a special edition in J. Phys. Cond. Mat as part of the proceedings of the HFM2006 conference in Osaka, Japan

We report the synthesis, crystal structure and magnetic properties of the S=1 2-leg spin-ladder compound Na_2Ni_2(C_2O_4)_3(H_2O)_2. The magnetic properties were examined by magnetic susceptibility and pulsed high field magnetization measurements. The magnetic excitations have been measured in high field high frequency ESR. Although the Ni(II) ions form structurally a 2-leg ladder, an isolated dimer model consistently describes the observations very well. The analysis of the temperature dependent magnetization data leads to a magnetic exchange constant of J=43 K along the rungs of the ladder and an average value of the g-factor of 2.25. From the ESR measurements, we determined the single ion anisotropy to D=11.5 K. The validity of the isolated dimer model is supported by Quantum Monte Carlo calculations, performed for several ratios of interdimer and intradimer magnetic exchange and taking into account the experimentally determined single ion anisotropy. The results can be understood in terms of the different coordination and superexchange angles of the oxalate ligands along the rungs and legs of the 2-leg spin ladder., Comment: 8 pages, 10 figures

Electron spin resonance and magnetization data in magnetic fields up to 55 T of a novel multicenter paramagnetic molecular complex [L_2Ni_4(N_3)(O_2C Ada)_4](Cl O_4) are reported. In this compound, four Ni centers each having a spin S = 1 are coupled in a single molecule via bridging ligands (including a \mu_4-azide) which provide paths for magnetic exchange. Analysis of the frequency and temperature dependence of the ESR signals yields the relevant parameters of the spin Hamiltonian, in particular the single ion anisotropy gap and the g factor, which enables the calculation of the complex energy spectrum of the spin states in a magnetic field. The experimental results give compelling evidence for tuning the ground state of the molecule by magnetic field from a nonmagnetic state at small fields to a magnetic one in strong fields owing to the spin level crossing at a field of ~25 T., Comment: revised version, accepted for publication in Physical Review B

We report an electron spin resonance (ESR) study of the s=1/2-Heisenberg pseudo-ladder magnet CaCu2O3 in pulsed magnetic fields up to 40 T. At sub-Terahertz frequencies we observe an ESR signal originating from a small amount of uncompensated spins residing presumably at the imperfections of the strongly antiferromagnetically correlated host spin lattice. The data give evidence that these few percent of ''extra'' spin states are coupled strongly to the bulk spins and are involved in the antiferromagnetic ordering at T_N = 25 K. By mapping the frequency/resonance field diagram we have determined a small gap for magnetic excitations below T_N of the order of 0.3 - 0.8 meV. Such a small value of the gap explains the occurrence of the spin-flop transition in CaCu2O 3 at weak magnetic fields H_{sf} ~ 3 T. Qualitative changes of the ESR response with increasing the field strength give indications that strong magnetic fields reduce the antiferromagnetic correlations and may even suppress the long-range magnetic order in CaCu2O3. ESR data support scenarios with a significant role of the ''extra'' spin states for the properties of low-dimensional quantum magnets., Comment: revised version, accepted for publication in the New Journal of Physics

High- and low-field magneto-transport measurements, as well as SQUID measurements of magnetization, were carried out on Ga1-xMnxAs epilayers grown by low temperature molecular beam epitaxy, and subsequently annealed under various conditions. We observe a large enhancement of ferromagnetism when the samples are annealed at an optimal temperature, typically about 280 0C. Such optimal annealing leads to an increase of Curie temperature, accompanied by an increase of both the conductivity and the saturation magnetization. A decrease of the coercive field and of magnetoresistivity is also observed for Ga1-xMnxAs annealed at optimal conditions. We suggest that the experimental results reported in this paper are related to changes in the domain structure of Ga1-xMnxAs., Comment: 2-nd International Conference on Physics and Application of Spin Related Phenomena In Semoconductors, Wurzburg 23-26 July 2002, to be published in a special issue of the Journal of Superconductivity/Novel Magnetism

The Anomalous Hall Effect was investigated in IV-VI ferromagnetic semimagnetic semiconductors of Sn1-xMnxTe codoped with either Eu or Er. The analysis of experimental data: Hall resisitivity and magnetization showed that AHE coefficient RS depends on temperature, its value decreases with the temperature increase. We observe that above ferromagnet-paramagnet transition temperature RS changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of RS, particularly change of the sign., Comment: 2nd International Conference on Physics and Application of Spin Related Phenomena In Semiconductors, Wurzburg 23-26 July 2002, to be published in aspecial issue of the Journal of Superconductivity/Novel Magnetism

We present the results of low temperature (LT) annealing studies of Ga1-xMnxAs epilayers grown by low temperature molecular beam epitaxy in a wide range of Mn concentrations (0.01

We measure the Hall conductivity, $\sigma_{xy}$, on a Corbino geometry sample of a high-mobility AlGaAs/GaAs heterostructure in a pulsed magnetic field. At a bath temperature about 80 mK, we observe well expressed plateaux in $\sigma_{xy}$ at integer filling factors. In the pulsed magnetic field, the Laughlin condition of the phase coherence of the electron wave functions is strongly violated and, hence, is not crucial for $\sigma_{xy}$ quantization., Comment: 4 pages, 4 figures, submitted to PRL