Magnetic and transport properties of i-RR-Cd icosahedral quasicrystals (RR = Y, Gd-Tm)

We present a detailed characterization of the recently discovered i-$R$-Cd ($R$ = Y, Gd-Tm) binary quasicrystals by means of x-ray diffraction, temperature-dependent dc and ac magnetization, temperature-dependent resistance and temperature-dependent specific heat measurements. Structurally, the broadening of x-ray diffraction peaks found for i-$R$-Cd is dominated by frozen-in phason strain, which is essentially independent of $R$. i-Y-Cd is weakly diamagnetic and manifests a temperature-independent susceptibility. i-Gd-Cd can be characterized as a spin-glass below 4.6 K via dc magnetization cusp, a third order non-linear magnetic susceptibility peak, a frequency-dependent freezing temperature and a broad maximum in the specific heat. i-$R$-Cd ($R$ = Ho-Tm) is similar to i-Gd-Cd in terms of features observed in thermodynamic measurements. i-Tb-Cd and i-Dy-Cd do not show a clear cusp in their zero-field-cooled dc magnetization data, but instead show a more rounded, broad local maximum. The resistivity for i-$R$-Cd is of order 300 $\mu \Omega$ cm and weakly temperature-dependent. The characteristic freezing temperatures for i-$R$-Cd ($R$ = Gd-Tm) deviate from the de Gennes scaling, in a manner consistent with crystal electric field splitting induced local moment anisotropy.Comment: 14 page

Learning from books

Alan H. Goldman on the philosophical value of the nove

Addressing the Inadequacies of Information Available on the Internet: The Prospect for a Technical Solution

In the past ten years the Internet has been the carrier and transmitter of vast amounts of information. Most of it has never been subjected to peer review or even casual review and has therefore been the source of misinformation. Additionally, there is need for more researchers to utilize critical thinking techniques of evaluating the credibility of sources. This paper chronicles my critical and creative thinking processes and results regarding these three areas of the information problems that are prevalent on the Internet. The first area is the problem of bad, biased or incorrect information including hoaxes and scams. I used critical thinking techniques to analyze these areas to provide a basis to define a problem to be solved. The second area of concern is the critical thinking process that should be used to evaluate the reliability of resources and the credibility of information. This process can help prevent the Internet user from being a victim of bad or biased information. The third area deals with similar problems of information that were solved both inside and outside the Internet that could provide bases for solutions. Here, I used critical thinking in regard to other possible outcomes. I discuss what other industries such as consumer product review companies and academia have done to deal with similar problems. I take a look at Underwriters Laboratories and others who devised systems that verified the quality of product as well as research methods that assure quality of information. I developed a conceptual framework for a software-based solution that can help assure that high quality information is presented on the Internet. I used a process of divergent and convergent thinking to arrive at a best solution. The solution allows for those who use the Internet data to leave information with or without leaving evaluation comments that describe the quality and usefulness of what was presented. The results of this user feedback are not only available to others who search for this information, but it can be presented in a prioritized form from most reviewed to least reviewed thus saving researchers time and effort while assuring a better quality of information

Twinned one-dimensional quasicrystals in Bridgman-grown Al-Si-Cu-Co alloys

Single grains of Al60Si2Cu18Co20 with a decaprismatic morphology were grown by the Bridgman method and studied by transmission electron microscopy and x-ray diffraction. Although the diffraction patterns of these grains superficially resemble that of a decagonal quasicrystal, a closer inspection reveals that they are composed of tenfold twins of a one-dimensional quasicrystal along with small domains of three crystalline approximant phases

Three Large-Scale Changes To The Medicare Program Could Curb Its Costs But Also Reduce Enrollment

With Medicare spending projected to increase to 24 percent of all federal spending and to equal 6 percent of the gross domestic product by 2037, policy makers are again considering ways to curb the program's spending growth. We used a microsimulation approach to estimate three scenarios: imposing a means-tested premium for Part A hospitalinsurance, introducing a premium support credit to purchase health insurance, and increasing the eligibility age to sixty-seven.We found thatthe scenarios would lead to reductions in cumulative Medicare spending in 2012 -- 36 of 2.4 -- 24.0 percent. However, the scenarios also would increase out-of-pocket spending for enrollees and, in some cases, causemillions of seniors not to enroll in the program and to be left without coverage. To achieve substantial cost savings without causing substantial lack of coverage among seniors, policy makers should consider benefitchanges in combination with other options, such as some of those now being contemplated by the Obama administration and Congress

Short-range magnetic correlations in Tb5Ge4

We present a single crystal neutron diffraction study of the magnetic short-range correlations in Tb$_5$Ge$_4$ which orders antiferromagnetically below the Neel temperature $T_N$ $\approx$ 92 K. Strong diffuse scattering arising from magnetic short-range correlations was observed in wide temperature ranges both below and above $T_N$. The antiferromagnetic ordering in Tb$_5$Ge$_4$ can be described as strongly coupled ferromagnetic block layers in the $ac$-plane that stack along the b-axis with weak antiferromagnetic inter-layer coupling. Diffuse scattering was observed along both $a^*$ and $b^*$ directions indicating three-dimensional short-range correlations. Moreover, the $q$-dependence of the diffuse scattering is Squared-Lorentzian in form suggesting a strongly clustered magnetic state that may be related to the proposed Griffiths-like phase in Gd$_5$Ge$_4$.Comment: 6 pages, 5 figure

Antiferromagnetic order in CaK(Fe[1-x]Ni[x])4As4 and its interplay with superconductivity

The magnetic order in CaK(Fe[1-x]Ni[x])4As4 (1144) single crystals (x = 0.051 and 0.033) has been studied by neutron diffraction. We observe magnetic Bragg peaks associated to the same propagation vectors as found for the collinear stripe antiferromagnetic (AFM) order in the related BaFe2As2 (122) compound. The AFM state in 1144 preserves tetragonal symmetry and only a commensurate, non-collinear structure with a hedgehog spin-vortex crystal (SVC) arrangement in the Fe plane and simple AFM stacking along the c direction is consistent with our observations. The SVC order is promoted by the reduced symmetry in the FeAs layer in the 1144 structure. The long-range SVC order coexists with superconductivity, however, similar to the doped 122 compounds, the ordered magnetic moment is gradually suppressed with the developing superconducting order parameter. This supports the notion that both collinear and non-collinear magnetism and superconductivity are competing for the same electrons coupled by Fermi surface nesting in iron arsenide superconductors.Comment: (5 pages, 5 figures

Anisotropy and large magnetoresistance in narrow gap semiconductor FeSb2

A study of the anisotropy in magnetic, transport and magnetotransport properties of FeSb2 has been made on large single crystals grown from Sb flux. Magnetic susceptibility of FeSb2 shows diamagnetic to paramagnetic crossover around 100K. Electrical transport along two axes is semiconducting whereas the third axis exhibits a metal - semiconductor crossover at temperature Tmin which is sensitive to current alignment and ranges between 40 and 80K. In H=70kOe semiconducting transport is restored for T<300K, resulting in large magnetoresistance [rho(70kOe)-rho(0)]/rho(0)=2200% in the crossover temperature rangeComment: 4 pages, 4 figures, Submitted to Phys. Rev.