Digital data transition tracking loop improves data reception

Transition tracking loop eliminates drifts, leakages, and instabilities inherent in analog filters. Major components are the phase detector, loop filter, voltage-controlled oscillator and timing logic

Unconventional Anomalous Hall Effect in the Metallic Triangular-Lattice Magnet PdCrO2

We experimentally reveal an unconventional anomalous Hall effect (UAHE) in a quasi-two-dimensional triangular-lattice antiferromagnet PdCrO2. Using high quality single crystals of PdCrO2, we found that the Hall resistivity deviates from the conventional behavior below T* = 20 K, noticeably lower than TN = 37.5 K, at which Cr^{3+} (S=3/2) spins order in a 120 degree structure. In view of the theoretical expectation that the spin chirality cancels out in the simplest 120 degree spin structure, we discuss required conditions for the emergence of UAHE within Berry-phase mechanisms.Comment: 4 pages, 5 figures, accepted for publication in PR

Synoptic studies in fog

This study of fog formations at Hadley Airport was carried out during the winter of 1928-29 with the intent of finding out how far a careful scrutiny of local records might assist in explaining and forecasting local fogs. It was meant to be supplementary to a more general discussion of fog and haze formation which had appeared previously in the Monthly Weather Review for November, 1928. This study is based on the general fog classification set forth there

American air mass properties

In this paper the term Air Mass is applied to an extensive portion of the earth's atmosphere which approximates horizontal homogeneity. The formation of an air mass in this sense takes place on the earth's surface wherever the atmosphere remains at rest over an extensive area of uniform surface properties for a suffciently long time so that the properties of the atmosphere (vertical distribution of temperature and moisture) reach equilibrium with respect to the surface beneath. Such a region on the earth's surface is referred to as a source region of air masses. As examples of source regions we might cite the uniformly snow and ice covered northern portion of the continent of North America in winter, or the uniformly warm waters of the Gulf of Mexico and Caribbean Sea. Obviously the properties of an air mass in the source region will depend entirely upon the nature of the source region. The concept of the air mass is of importance not only in the source regions. Sooner or later a general movement of the air mass from the source region is certain to occur, as one of the large-scale air currents which we find continually moving across the synoptic charts. Because of the great extent of such currents and the conservatism of the air mass properties, it is usually easy to trace the movement of the air mass from day to day, while at the same time any modification of its properties by its new environment can be carefully noted. Since this modification is not likely to be uniform throughout the entire air mass, it may to a certain degree destroy the horizontal homogeneity of the mass. However, the horizontal differences produced within an air mass in this manner are small and continuous in comparison to the abrupt and discontinuous transition zones, or fronts, which mark the boundaries between air masses. Frontal discontinuities are intensified wherever there is found in the atmosphere convergent movement of air masses of different properties. Since the air masses from particular sources are found to possess at any season certain characteristic properties which undergo rather definite modification depending upon the trajectory of the air mass after leaving its source region, the investigation of the characteristic properties of the principal air mass types can be of great assistance to the synoptic meteorologist and forecaster. We owe this method of attack on the problems of synoptic meteorology to the Norwegian school of meteorologists, notably to T. Bergeron. Investigation of the properties of the principal air masses appearing in western Europe has been made in particular by O. Moese and G. Schinze. The purpose of this paper is to give the results of a similar investigation of the properties of the principal air masses of North America, and to comment on some of the striking differences which appear between conditions here and in Europe

Discussion and illustration of problems suggested by the analysis of atmospheric cross-sections

The preparation of atmospheric cross-sections, in which the fields of the various meteorological elements are represented in the vertical plane containing a number of synoptic aerological soundings, has long been a part of the technique applied to the investigation of problems in synoptic meteorology. However, owing to the lack of adequate observational material, the number of such cross-sections prepared in the past has been very small. The method was applied only in a few cases chosen for careful analysis and study. Consequently no uniform technique of analysis of such cross-sections has been developed, nor have the possibilities of this method of synoptic investigation received much attention. In the fall of 1933 the author decided that the possibilities of the cross-section method of synoptic representation warranted the systematic preparation and analysis of a large number of cross-sections. For this purpose a number of periods during which the synoptic maps seemed to indicate interesting atmospheric developments, and for which numerous aerological observations were available, were chosen from the maps of the preceding two or three years for detailed cross-sectional study. In all, ten periods of from two to six days each were chosen, a total of 36 days, entailing the preparation of about 90 cross-sections, and the use of about 400 aerological soundings

Anomalous Fermi Liquid Behavior of Overdoped High-Tc Superconductors

According to a generic temperature vs. carrier-doping (T-p) phase diagram of high-temperature superconductors it has been proposed that as doping increases to the overdoped region they approach gradually a conventional (canonical) Fermi Liquid. However, Hall effect measurements in several systems reported by different authors show a still strong \emph{T}-dependence in overdoped samples. We report here electrical transport measurements of Y_{1-x}Ca_{x}Ba_{2}Cu_{3}O_{7-delta} thin films presenting a temperature dependence of the Hall constant, R_H, which does not present a gradual transition towards the T-independent behavior of a canonical Fermi Liquid. Instead, the T-dependence passes by a minimum near optimal doping and then increases again in the overdoped region. We discuss the theoretical predictions from two representative Fermi Liquid models and show that they can not give a satisfactory explanation to our data. We conclude that this region of the phase diagram in YBCO, as in most HTSC, is not a canonical Fermi Liquid, therefore we call it Anomalous Fermi Liquid.Comment: 9 pages, 12 figures, to be published in Phys. Rev.

Asymmetric field dependence of magnetoresistance in magnetic films

We study an asymmetric in field magnetoresistance that is frequently observed in magnetic films and, in particular, the odd longitudinal voltage peaks that appear during magnetization reversal in ferromagnetic films, with out-of-plane magnetic anisotropy. We argue that the anomalous signals result from small variation of magnetization and Hall resistivity along the sample. Experimental data can be well described by a simple circuit model, the latter being supported by analytic and numerical calculations of current and electric field distribution in films with a gradual variation of the magnetization and Hall resistance.Comment: 7 pages, 5 figures, to be published in Phys. Rev.

A hidden constant in the anomalous Hall effect of a high-purity magnet MnSi

Measurements of the Hall conductivity in MnSi can provide incisive tests of theories of the anomalous Hall (AH) effect, because both the mean-free-path and magnetoresistance (MR) are unusually large for a ferromagnet. The large MR provides an accurate way to separate the AH conductivity $\sigma_{xy}^A$ from the ordinary Hall conductivity $\sigma_{xy}^N$. Below the Curie temperature $T_C$, $\sigma_{xy}^A$ is linearly proportional to $M$ (magnetization) with a proportionality constant $S_H$ that is independent of both $T$ and $H$. In particular, $S_H$ remains a constant while $\sigma_{xy}^N$ changes by a factor of 100 between 5 K and $T_C$. We discuss implications of the hidden constancy in $S_H$.Comment: 5 pages, 4 figures. Minor change

Superconducting d-wave junctions: The disappearance of the odd ac components

We study voltage-biased superconducting planar d-wave junctions for arbitrary transmission and arbitrary orientation of the order parameters of the superconductors. For a certain orientation of the superconductors the odd ac components disappear, resulting in a doubling of the Josephson frequency. We study the sensitivity of this disappearance to orientation and compare with experiments on grain boundary junctions. We also discuss the possibility of a current flow parallel to the junction.Comment: 5 pages, 3 figure

Intrinsic vs. extrinsic anomalous Hall effect in ferromagnets

A unified theory of the anomalous Hall effect (AHE) is presented for multi-band ferromagnetic metallic systems with dilute impurities. In the clean limit, the AHE is mostly due to the extrinsic skew-scattering. When the Fermi level is located around anti-crossing of band dispersions split by spin-orbit interaction, the intrinsic AHE to be calculated ab initio is resonantly enhanced by its non-perturbative nature, revealing the extrinsic-to-intrinsic crossover which occurs when the relaxation rate is comparable to the spin-orbit interaction energy.Comment: 5 pages including 4 figures, RevTex; minor changes, to appaer in Phys. Rev. Let