Radial gradients and anisotropies of cosmic rays in the interplanetary medium

Radial gradients and anisotropies of cosmic rays in interplanetary mediu

Magnetotransport in the low carrier density ferromagnet EuB_6

We present a magnetotransport study of the low--carrier density ferromagnet EuB_6. This semimetallic compound, which undergoes two ferromagnetic transitions at T_l = 15.3 K and T_c = 12.5 K, exhibits close to T_l a colossal magnetoresistivity (CMR). We quantitatively compare our data to recent theoretical work, which however fails to explain our observations. We attribute this disagreement with theory to the unique type of magnetic polaron formation in EuB_6.Comment: Conference contribution MMM'99, San Jos

Magnetic measurements at pressures above 10 GPa in a miniature ceramic anvil cell for a superconducting quantum interference device magnetometer

A miniature ceramic anvil high pressure cell (mCAC) was earlier designed by us for magnetic measurements at pressures up to 7.6 GPa in a commercial superconducting quantum interference (SQUID) magnetometer [N. Tateiwa et al., Rev. Sci. Instrum. 82, 053906 (2011)]. Here, we describe methods to generate pressures above 10 GPa in the mCAC. The efficiency of the pressure generation is sharply improved when the Cu-Be gasket is sufficiently preindented. The maximum pressure for the 0.6 mm culet anvils is 12.6 GPa when the Cu-Be gasket is preindented from the initial thickness of 0.30 to 0.06 mm. The 0.5 mm culet anvils were also tested with a rhenium gasket. The maximum pressure attainable in the mCAC is about 13 GPa. The present cell was used to study YbCu2Si2 which shows a pressure induced transition from the non-magnetic to magnetic phases at 8 GPa. We confirm a ferromagnetic transition from the dc magnetization measurement at high pressure. The mCAC can detect the ferromagnetic ordered state whose spontaneous magnetic moment is smaller than 1 mB per unit cell. The high sensitivity for magnetic measurements in the mCAC may result from the the simplicity of cell structure. The present study shows the availability of the mCAC for precise magnetic measurements at pressures above 10 GPa

A New Heavy-Fermion Superconductor CeIrIn5: Relative of the Cuprates?

CeIrIn5 is a member of a new family of heavy-fermion compounds and has a Sommerfeld specific heat coefficient of 720 mJ/mol-K2. It exhibits a bulk, thermodynamic transition to a superconducting state at Tc=0.40 K, below which the specific heat decreases as T2 to a small residual T-linear value. Surprisingly, the electrical resistivity drops below instrumental resolution at a much higher temperature T0=1.2 K. These behaviors are highly reproducible and field-dependent studies indicate that T0 and Tc arise from the same underlying electronic structure. The layered crystal structure of CeIrIn5 suggests a possible analogy to the cuprates in which spin/charge pair correlations develop well above Tc

Aquatic Animal Health Training Scheme. Fish disease diagnosis, biosecurity & disease management training for fish farming industry of Australia.

This workshop delivered new knowledge and technical skills with hands-on training to 24 participants representing of Australian fish-farming and government veterinarian sectors. The workshop focused on delivering training in both theory and practical aspects, with delivering hands-on technical skills, relating directly to fish disease detection, diagnosis, treatment, control, disease emergency response, disease reporting, fish health certification, fish toxicology and fish kills. The workshop was held in Townsville, Queensland on July 17th-18th, 2015, and was organized and delivered by Dr Rachel Bowater, Mr Andrew Fisk, Dr Kitman Dyrting, Dr Ian Anderson and Dr Roger Chong, with whom collectively have >100 years of experience in fish diagnostics, research, pathology, policy and aquaculture extension

Distinct order of Gd 4f and Fe 3d moments coexisting in GdFe4Al8

Single crystals of flux-grown tetragonal GdFe4Al8 were characterized by thermodynamic, transport, and x-ray resonant magnetic scattering measurements. In addition to antiferromagnetic order at TN ~ 155 K, two low-temperature transitions at T1 ~ 21 K and T2 ~ 27 K were identified. The Fe moments order at TN with an incommensurate propagation vector (tau,tau,0) with tau varying between 0.06 and 0.14 as a function of temperature, and maintain this order over the entire T<TN range. The Gd 4f moments order below T2 with a ferromagnetic component mainly out of plane. Below T1, the ferromagnetic components are confined to the crystallographic plane. Remarkably, at low temperatures the Fe moments maintain the same modulation as at high temperatures, but the Gd 4f moments apparently do not follow this modulation. The magnetic phase diagrams for fields applied in [110] and [001] direction are presented and possible magnetic structures are discussed.Comment: v2: 14 pages, 12 figures; PRB in prin

Magnetic Structure of Rapidly Rotating FK Comae-Type Coronae

We present a three-dimensional simulation of the corona of an FK Com-type rapidly rotating G giant using a magnetohydrodynamic model that was originally developed for the solar corona in order to capture the more realistic, non-potential coronal structure. We drive the simulation with surface maps for the radial magnetic field obtained from a stellar dynamo model of the FK Com system. This enables us to obtain the coronal structure for different field topologies representing different periods of time. We find that the corona of such an FK Com-like star, including the large scale coronal loops, is dominated by a strong toroidal component of the magnetic field. This is a result of part of the field being dragged by the radial outflow, while the other part remains attached to the rapidly rotating stellar surface. This tangling of the magnetic field,in addition to a reduction in the radial flow component, leads to a flattening of the gas density profile with distance in the inner part of the corona. The three-dimensional simulation provides a global view of the coronal structure. Some aspects of the results, such as the toroidal wrapping of the magnetic field, should also be applicable to coronae on fast rotators in general, which our study shows can be considerably different from the well-studied and well-observed solar corona. Studying the global structure of such coronae should also lead to a better understanding of their related stellar processes, such as flares and coronal mass ejections, and in particular, should lead to an improved understanding of mass and angular momentum loss from such systems.Comment: Accepted to ApJ, 10 pages, 6 figure

Electron transport, penetration depth and upper critical magnetic field of ZrB12 and MgB2

We report on the synthesis and measurements of the temperature dependence of resistivity, R(T), the penetration depth, l(T), and upper critical magnetic field, Hc2(T), for polycrystalline samples of dodecaboride ZrB12 and diboride MgB2. We conclude that ZrB12 as well as MgB2 behave like simple metals in the normal state with usual Bloch-Gruneisen temperature dependence of resistivity and with rather low resistive Debye temperature, TR=280 K, for ZrB12 (as compared to MgB2 with TR=900 K). The R(T) and l(T) dependencies of ZrB12 reveal a superconducting transition at Tc=6.0 K. Although a clear exponential l(T)dependence in MgB2 thin films and ceramic pellets was observed at low temperatures, this dependence was almost linear for ZrB12 below Tc/2. These features indicate s-wave pairing state in MgB2, whereas a d-wave pairing state is possible in ZrB12. A fit to the data gives a reduced energy gap 2D(0)/kTc=1.6 for MgB2 films and pellets, in good agreement with published data for 3D \pi - sheets of the Fermi surface. Contrary to conventional theories we found a linear temperature dependence of Hc2(T) for ZrB12 (Hc2(0)=0.15 T).Comment: 8 pages, 10 figures, submitted to JET

Tuning Low Temperature Physical Properties of CeNiGe3_{3} by Magnetic Field

We have studied the thermal, magnetic, and electrical properties of the ternary intermetallic system CeNiGe$_{3}$ by means of specific heat, magnetization, and resistivity measurements. The specific heat data, together with the anisotropic magnetic susceptibility, was analyzed on the basis of the point charge model of crystalline electric field. The $J$\,=\,5/2 multiplet of the Ce$^{3+}$ is split by the crystalline electric field (CEF) into three Kramers doublets, where the second and third doublet are separated from the first (ground state) doublet by $\Delta_{1}$ $\sim$ 100\,K and $\Delta_{2}$ $\sim$ 170\,K, respectively. In zero field CeNiGe$_{3}$ exhibits an antiferromangeic order below $T_{N}$ = 5.0\,K. For \textbf{H}\,$\parallel$\,\textbf{a} two metamagnetic transitions are clearly evidenced between 2\,$\sim$\,4\,K from the magnetization isotherm and extended down to 0.4\,K from the magnetoresistance measurements. For \textbf{H}\,$\parallel$\,\textbf{a}, $T_{N}$ shifts to lower temperature as magnetic field increases, and ultimately disappears at $H_{c}$ $\sim$ 32.5\,kOe. For $H\,>\,H_{c}$, the electrical resistivity shows the quadratic temperature dependence ($\Delta\rho = A T^{2}$). For $H \gg H_{c}$, an unconventional $T^{n}$-dependence of $\Delta\rho$ with $n > 2$ emerges, the exponent $n$ becomes larger as magnetic field increases. Although the antiferromagnetic phase transition temperature in CeNiGe$_{3}$ can be continuously suppressed to zero, it provides an example of field tuning that does not match current simple models of Quantum criticality.Comment: accepted PR