Current-driven thermo-magnetic switching in magnetic tunnel junctions

We investigate switching of magnetic tunnel junctions (MTJs) driven by the thermal effect of the transport current through the junctions. The switching occurs in a specially designed composite free layer, which acts as one of the MTJ electrodes, and is due to a current-driven ferro-to-paramagnetic Curie transition with the associated exchange decoupling within the free layer leading to magnetic reversal. We simulate the current and heat propagation through the device and show how heat focusing can be used to improve the power efficiency. The Curie-switch MTJ demonstrated in this work has the advantage of being highly tunable in terms of its operating temperature range, conveniently to or just above room temperature, which can be of technological significance and competitive with the known switching methods using spin-transfer torques.Comment: 5 pages, 3 figure

Resistivity studies under hydrostatic pressure on a low-resistance variant of the quasi-2D organic superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br: quest for intrinsic scattering contributions

Resistivity measurements have been performed on a low (LR)- and high (HR)-resistance variant of the kappa-(BEDT-TTF)_2Cu[N(CN)_2]Br superconductor. While the HR sample was synthesized following the standard procedure, the LR crystal is a result of a somewhat modified synthesis route. According to their residual resistivities and residual resistivity ratios, the LR crystal is of distinctly superior quality. He-gas pressure was used to study the effect of hydrostatic pressure on the different transport regimes for both variants. The main results of these comparative investigations are (i) a significant part of the inelastic-scattering contribution, which causes the anomalous rho(T) maximum in standard HR crystals around 90 K, is sample dependent, i.e. extrinsic in nature, (ii) the abrupt change in rho(T) at T* approx. 40 K from a strongly temperature-dependent behavior at T > T* to an only weakly T-dependent rho(T) at T < T* is unaffected by this scattering contribution and thus marks an independent property, most likely a second-order phase transition, (iii) both variants reveal a rho(T) proportional to AT^2 dependence at low temperatures, i.e. for T_c < T < T_0, although with strongly sample-dependent coefficients A and upper bounds for the T^2 behavior measured by T_0. The latter result is inconsistent with the T^2 dependence originating from coherent Fermi-liquid excitations.Comment: 8 pages, 6 figure

Evolved star water maser cloud size determined by star size

Cool, evolved stars undergo copious mass loss but the details of how the matter is returned to the ISM are still under debate. We investigated the structure and evolution of the wind at 5 to 50 stellar radii from Asymptotic Giant Branch and Red Supergiant stars. 22-GHz water masers around seven evolved stars were imaged using MERLIN, at sub-AU resolution. Each source was observed at between 2 and 7 epochs (several stellar periods). We compared our results with long-term Pushchino single dish monitoring. The 22-GHz emission is located in ~spherical, thick, unevenly filled shells. The outflow velocity doubles between the inner and outer shell limits. Water maser clumps could be matched at successive epochs separated by <2 years for AGB stars, or at least 5 years for RSG. This is much shorter than the decades taken for the wind to cross the maser shell, and comparison with spectral monitoring shows that some features fade and reappear. In 5 sources, most of the matched features brighten or dim in concert from one epoch to the next. One cloud in W Hya was caught in the act of passing in front of a background cloud leading to 50-fold, transient amplification. The masing clouds are 1-2 orders of magnitude denser than the wind average and contain a substantial fraction of the mass loss in this region, with a filling factor <1%. The RSG clouds are ~10x bigger than those round the AGB stars. Proper motions are dominated by expansion, with no systematic rotation. The maser clouds survive for decades (the shell crossing time) but the masers are not always beamed in our direction. Radiative effects cause changes in flux density throughout the maser shells on short timescales. Cloud size is proportional to parent star size; clouds have a similar radius to the star in the 22-GHz maser shell. Stellar properties such as convection cells must determine the clumping scale.Comment: Accepted by A&A 2012 July 10 Main text 29 pages, 62 figures Appendix 44 pages, 23 figure

DAMPAK WISATAWAN ASING TERHADAP PERUBAHAN SOSIAL BUDAYA MASYARAKAT (STUDI PADA MASYARAKAT DI KEC. LHOKNGA KAB. ACEH BESAR)

ABSTRAKBerkembangnya pariwisata di tengah masyarakat membawa pengaruh terhadap kehidupan sosial budaya. Pariwisata selalu mempertemukan dua atau lebih kebudayaan yang akan menghasilkan berbagai proses perubahan seperti akulturasi, dominasi, asimilasi, adopsi, adaptasi dan sebagainya. Wisatawan mancanegara yang berkunjung ke Lhoknga telah membawa pengaruh terhadap masyarakat lokal di daerah sekitar objek wisata. Penelitian ini bertujuan untuk mengetahui dampak pariwisata terhadap perubahan sosial budaya masyarakat dan mengetahui bentuk perubahan sosial budaya yang terjadi pada masyarakat Lhoknga akibat perkembangan pariwisata di Mukim Lhoknga. Metodologi penelitian ini menggunakan pendekatan kualitatif dengan model studi deskriptif. Pengumpulan data dilakukan dengan wawancara mendalam dan observasi. Dari hasil penelitian menunjukkan bahwa terjadinya perubahan sosial budaya pada masyarakat lokal di Mukim Lhoknga, Kecamatan Lhoknga Kabupaten Aceh Besar. Namun perubahan yang dimaksud masih dikategorikan perubahan secara mikro, karena tidak membawa pengaruh yang mendalam pada kehidupan masyarakat lokal. Dampak pariwisata terhadap perubahan sosial budaya masyarakat dapat dipilah menjadi dua yaitu dampak positif dan dampak negatif. Dampak positifnya yaitu dengan adanya pariwisata telah membuka lapangan kerja baru bagi masyarakat lokal yang dapat meningkatkan pendapatan ekonomi, mampu menguasai bahasa asing, seperti bahasa Inggris, Jepang. Terbukanya akses bagi masyarakat lokal ke jaringan yang lebih luas, memperlihatkan keindahan alam dan budaya yang tak lepas dari rasa untuk meningkatkan persaudaraan dalam lingkungan nasional dan internasional Sedangkan dampak negatif yaitu, lunturnya budaya lokal (tradisional) akibat masuknya budaya luar (modern). Adapun bentuk-bentuk perubahan dapat dilihat dari dua segi yaitu perubahan segi sosial dan perubahan dari segi budaya. Bentuk perubahan dari segi sosial yaitu terjadinya perubahan struktur sosial masyarakat lokal dengan beralihnya sektor pekerjaan dari petani atau nelayan ke sektor industri, Meningkatnya keinginan untuk berpendidikan tinggi, sedangkan perubahan dari segi budaya yaitu terjadinya perkawinan dari dua unsur budaya yang berbeda, perubahan pada penggunaan bahasa, perubahan cara berpakaian dan perubahan perilaku dalam keluarga.Kata Kunci : Pariwisata, Wisatawan Asing, Perubahan Sosial, Perubahan Budaya.Banda Ace

Thermal and magnetic properties of integrable spin-1 and spin-3/2 chains with applications to real compounds

The ground state and thermodynamic properties of spin-1 and spin-3/2 chains are investigated via exactly solved su(3) and su(4) models with physically motivated chemical potential terms. The analysis involves the Thermodynamic Bethe Ansatz and the High Temperature Expansion (HTE) methods. For the spin-1 chain with large single-ion anisotropy, a gapped phase occurs which is significantly different from the valence-bond-solid Haldane phase. The theoretical curves for the magnetization, susceptibility and specific heat are favourably compared with experimental data for a number of spin-1 chain compounds. For the spin-3/2 chain a degenerate gapped phase exists starting at zero external magnetic field. A middle magnetization plateau can be triggered by the single-ion anisotropy term. Overall, our results lend further weight to the applicability of integrable models to the physics of low-dimensional quantum spin systems. They also highlight the utility of the exact HTE method.Comment: 38 pages, 15 figure

Change of Organizational and Production Paradigms in the IT Industry: Research 2020–2023

The experience of creating successful geographically distributed engineering teams and the COVID pandemic have made a significant contribution to the dynamics of changing the organizational and production paradigm in the IT industry from the traditional 40-hour office work to a “hybrid” work week and even to completely remote software and IT-services development. In this study, the scientific task of determining the nature of the process of paradigm shift is set and a set of scientific hypotheses is set to identify fully remote work as an established practice for a significant number of leading IT companies in Europe. To test these hypotheses, thematic industry studies of 2020–2023 were analyzed, which convincingly proved that the forced transition to completely remote development during lockdown periods and after reducing the impact of pandemic risks becomes a conscious choice: in demand, economically rational, supported by a significant number of engineers and managers in the industry. At the same time, a “hybrid” work week, combining part of the days in the office and part outside it, has also remained a popular option for organizing work in IT companies and organizations with large teams for internal automation

Russian local trends in software development and implementation

Regulators of the Russian software market over the past five years have a significant impact on the market: from the serious requirements about the protection of personal data in information systems to the policy of import substitution. This article contains a part of the results of the author’s research that covered 79 experienced engineers and managers in all federal districts of Russia. The expert’s panel reviewed the change in costs and efforts in software development projects connected with stricter requirements for collecting and storing personal data, evaluated import substitution of system and application software and determined the possibilities of using technologies, based on open-source code. The results of the study are accompanied by brief recommendations of the author

Managing the Costs of Constant Changes in the Activities of High-Tech Enterprises

This article considers the solution of the actual scientifc and practical task of managing the costs of planning and implementing organizational and production changes at enterprises from high-tech industries. The authors present a modifcation of M. Porter’s model of competitive forces for high-tech industries and single out a separate managerial function — constant management of timely changes. The article considers the function of cost management, compares two approaches to change management and gives recommendations for optimization of corresponding costs taking into account the cost of management errors