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Abstract. A brief introduction to the ABINIT software package is given. Available under a free software license, it allows to compute directly a large set of properties useful for solid state studies, including structural and elastic properties, prediction of phase (meta)stability or instability, specific heat and free energy, spectroscopic and vibrational properties. These are described, and corresponding applications are presented. The emphasis is also laid on its ease of use and extensive documentation, allowing newcomers to quickly step in.

ABINIT is a package whose main program allows one to find the total energy, charge density, electronic structure and many other properties of systems made of electrons and nuclei, (molecules and periodic solids) within Density Functional Theory (DFT), Many-Body Perturbation Theory (GW approximation and Bethe-Salpeter equation) and Dynmical Mean Field Theory (DMFT). ABINIT also allows to optimize the geometry according to the DFT forces and stresses, to perform molecular dynamics simulations using these forces, and to generate dynamical matrices, Born effective charges and dielectric tensors. The present paper aims to describe the new capabilities of ABINIT that have been developed since 2009. It covers both physical and technical developments inside the ABINIT code, as well as developments provided within the ABINIT package. The developments are described with relevant references, input variables, tests and tutorials.

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We have prepared by electrodeposition Ni80Fe20/Cu multilayered nanowires into the pores of polymer membranes and performed giant magnetoresistance (GMR) measurements in the current perpendicular to the layer planes geometry. GMR ratios as high as 80% have been obtained at 4.2 K. Two types of structure have been studied: conventional Ni80Fe20/Cu multilayers and multilayers composed of Ni80Fe20/Cu/Ni80Fe20 trilayers magnetically isolated by long Cu rods.

Thermal measurements on a GaAs͞AlGaAs heterostructure reveal that the state of the confined twodimensional electrons profoundly affects the nuclear-spin diffusion near Landau level filling factor n 1. The experiments provide quantitative evidence that a dramatic enhancement of nuclear-spin diffusion from the GaAs quantum wells into the AlGaAs barriers is responsible for the recently reported sharp peak in the temperature dependence of heat capacity near n 1. We discuss the physical origin of this behavior in terms of the possible Skyrme solid-liquid phase transition. [S0031-9007(97)03939-2] PACS numbers: 73.20.Dx, 65.40. + g, 73.40.Hm In the presence of a perpendicular magnetic field (B), two-dimensional electron systems (2DESs) exhibit striking phenomena originating from the Landau quantization and electron-electron interaction; examples are the integral and fractional quantum Hall effects [1]. At Landau level filling factor n 1, theoretical work on 2DESs in GaAs͞AlGaAs heterostructures has shown that electron spin textures known as Skyrmions are the lowest energy, charged excitations of the ferromagnetic ground state [2]. Skyrmions, which result from the dominance of the electron-electron exchange energy over the Zeeman energy, are also the lowest energy state for quasiholes and quasielectrons near n 1; the ground state of a 2DES near n 1 is, in fact, expected to be a crystal of Skyrmions [3][4][5].Recent experimental studies have revealed that Skyrmions play a major role in many properties of quantum Hall systems [6][7][8][9]. In particular, measurements on a GaAs͞AlGaAs multiple-quantum-well (QW) heterostructure indicated an anomalous behavior for the low-temperature apparent heat capacity (C) near n 1: C is enhanced by a factor of up to ϳ10 5 with respect to its low-B value [9]. For temperatures T * 0.1 K, the magnitude as well as T and B dependence of the data are consistent with the large C being dominated by the Schottky nuclear heat capacity of Ga and As atoms in the QWs. This observation implies a strong enhancement of the nuclear spin-lattice relaxation rate near n 1, consistent with the results of nuclear magnetic resonance (NMR) experiments [6,7] and recent calculations which attribute the enhancement to the presence of low-energy spin-flip excitations in the 2DES [5]. An even more striking feature of the C vs T data is a very sharp peak at a very low temperature T c ͑n͒, suggestive of a phase transition in the 2DES [9]. While recent estimates for the melting temperature of the Skyrme crystal [4,5], including its dependence on n, suggest that the peak in C could originate from a Skyrme solid-liquid phase transition, the physical mechanism that affects the nuclear-spin dynamics and gives rise to the anomalous C peak is not known and is a matter of debate [4,5,9].In this Letter we report new quasiadiabatic thermal experiments revealing that the mechanism responsible for the peak in C vs T is a dramatic enhancement of nuclearspin diffusion across the QW-barrier interface. While only the nuclear heat ...

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