Current-induced torques due to compensated antiferromagnets

We analyse the influence of current induced torques on the magnetization configuration of a ferromagnet in a circuit containing a compensated antiferromagnet. We argue that these torques are generically non-zero and support this conclusion with a microscopic NEGF calculation for a circuit containing antiferromagnetic NiMn and ferromagnetic Co layers. Because of symmetry dictated differences in the form of the current-induced torque, the phase diagram which expresses the dependence of ferromagnet configuration on current and external magnetic field differs qualitatively from its ferromagnet-only counterpart.Comment: 4 pages, 5 figure

Data File Security Through Cryptography Using the Advanced Encryption Standard (RIJNDAEL): Working Paper Series--05-03

The use of cryptography, both the encryption and decryption of data is one response to the concerns of securing data files. The Rijndael cipher block, which has been adopted by the National Institute of Standards and technology as the advanced encryption standard, has been used in this study to encrypt and decrypt data. This has been accomplished by encrypting a plain text file and creating an encrypted file in one program, and decrypting the encrypted file back to a plain text file in another program. Both the encryption and decryption programs utilize the same secret key. If the key is lost decryption is not possible, and if the key is discovered the security of the data is compromised. Despite the risk, cryptography using the Rijndael cipher block adds considerable security to otherwise unsecured data

Something Lost - Something Gained: From COBOL to Java to C# in Intermediate Programming Courses: Working Paper Series--03-05

The decision as to which programming language to use in intermediate business programming courses has become increasingly challenging. For many years COBOL has been the language used, but recently Java has become the language of choice. This has come with the benefit of the use of a language that is fully object-oriented, but has also come with some costs. Among the costs is a more awkward Graphical User Interface, but the primary cost is the loss of the scope of data file processing that existed with COBOL. The use of C# in intermediate programming courses provides all of the benefits of Java, as far as object-orientation, and also provides the data file processing available in COBOL, but with a much more intuitive Graphical User Interface. What was lost by going from COBOL to Java has been regained by going from Java to C

.NET as a Teaching Tool: Working Paper Series--03-06

In the introductory business programming courses, the BASIC programming language was used for many years followed by Visual Basic more recently. In the intermediate and advanced business programming courses COBOL has been the language used for decades, but it has been replaced by Java more recently. This has come with the benefit of the use of objects, but has also come with the costs of a more awkward Graphical User Interface, and more cumbersome data file management than with COBOL. The use of .NET as a teaching tool solves this problem. The shift from VB to VB.NET in the introductory programming courses is a natural one, and the use of C# in the intermediate programming courses addresses the unwieldy nature of data file management in Java, but retains the benefits of object-orientation. The Graphical User Interface available in Visual Basic is retained in VB.NET, which is available for all languages used within .NET, including C#. The .NET development environment offers a seamless development environment for both introductory and intermediate programming courses

Current induced torques and interfacial spin-orbit coupling: Semiclassical Modeling

In bilayer nanowires consisting of a ferromagnetic layer and a non-magnetic layer with strong spin-orbit coupling, currents create torques on the magnetization beyond those found in simple ferromagnetic nanowires. The resulting magnetic dynamics appear to require torques that can be separated into two terms, damping-like and field-like. The damping-like torque is typically derived from models describing the bulk spin Hall effect and the spin transfer torque, and the field-like torque is typically derived from a Rashba model describing interfacial spin-orbit coupling. We derive a model based on the Boltzmann equation that unifies these approaches. We also consider an approximation to the Boltzmann equation, the drift-diffusion model, that qualitatively reproduces the behavior, but quantitatively fails to reproduce the results. We show that the Boltzmann equation with physically reasonable parameters can match the torques for any particular sample, but in some cases, it fails to describe the experimentally observed thickness dependences

COBOL.NET Running Legacy COBOL Programs by Proxy: Working Paper Series--05-02

One response to the trend toward object orientation in programming languages has been the inclusion of object orientation to COBOL. Additionally, graphical user interfaces have been added to existing batch and interactive COBOL programs. This has been accomplished through COBOL compilers and the addition of GUIs created in other languages. An expansion of both of these additions to legacy COBOL programs has been the incorporation of COBOL into Microsoft's .NET Framework. Through this process old legacy COBOL programs can appear as if they were written in a contemporary language such as C#

Current-induced torques and interfacial spin-orbit coupling

In bilayer systems consisting of an ultrathin ferromagnetic layer adjacent to a metal with strong spin-orbit coupling, an applied in-plane current induces torques on the magnetization. The torques that arise from spin-orbit coupling are of particular interest. Here, we calculate the current-induced torque in a Pt-Co bilayer to help determine the underlying mechanism using first principles methods. We focus exclusively on the analogue to the Rashba torque, and do not consider the spin Hall effect. The details of the torque depend strongly on the layer thicknesses and the interface structure, providing an explanation for the wide variation in results found by different groups. The torque depends on the magnetization direction in a way similar to that found for a simple Rashba model. Artificially turning off the exchange spin splitting and separately the spin-orbit coupling potential in the Pt shows that the primary source of the "field-like" torque is a proximate spin-orbit effect on the Co layer induced by the strong spin-orbit coupling in the Pt.Comment: 7 pages, 8 figure

Creating web services using ASP.NET: Working paper series--04-06

Web services have been advertised as the answer to enterprise application integration, reusability, and as a way to prolong the life of legacy applications. By developing applications as Web Services they become available (exposed) to other applications that use (consume) the service following open Web standards. These services can be exposed and consumed over an intranet, extranet, or the internet through standard Web technologies. These technologies include WSDL, an XML-based description format; SOAP, an application messaging protocol; and HTTP, a collection and transport protocol. Several simple Web Services were developed using ASP.NET technology. The Web Service applications were created using Visual Studio .NET. The services were published to a .NET server. A Web application was developed using Visual Studio .NET to consume the previously created Web Services. A definition of Web Services and descriptions of the technology that is used to create, expose, and consume the Web Services will be provided

Zero-Field Quantum Critical Point in Ce0.91_{0.91}Yb0.09_{0.09}CoIn5_5

We present results of specific heat, electrical resistance, and magnetoresistivity measurements on single crystals of the heavy-fermion superconducting alloy Ce$_{0.91}$Yb$_{0.09}$CoIn$_5$. Non-Fermi liquid to Fermi liquid crossovers are clearly observed in the temperature dependence of the Sommerfeld coefficient $\gamma$ and resistivity data. Furthermore, we show that the Yb-doped sample with $x=0.09$ exhibits universality due to an underlying quantum phase transition without an applied magnetic field by utilizing the scaling analysis of $\gamma$. Fitting of the heat capacity and resistivity data based on existing theoretical models indicates that the zero-field quantum critical point is of antiferromagnetic origin. Finally, we found that at zero magnetic field the system undergoes a third-order phase transition at the temperature $T_{c3}\approx 7$ K.Comment: 5 pages + 3 figures (main text) & 5 pages + 4 figures (supplementary materials