1,720,966 research outputs found
2D Ising Model MC Data
No full textDataset supporting:
Waters, J. M. et al (2017). Identification of Curie temperature distributions in magnetic particulate systems. Journal Of Physics D.
Results of Monte Carlo simulations of the 2D Ising model using disordered grains. Subfolders are labelled according to the size or distribution of sizes that are modelled, within those folders are the samples at different temperatures. The first column is magnetisation, the second is energy, the third is number of total spins.</span
Skyrmion MC Data
No full textMagnetisation, energy, skyrmion number and spin alignment measurements from Monte Carlo simulations of a disctetised skyrmion model. Files are in HDF5 format with tables containing the raw data.
This dataset supports the thesis "Finite-Size Scaling of Complex Materials Near the Phase Transition" by Jonathon Waters
This dataset can be requested via http://library.soton.ac.uk/datarequest’ </span
FePt MC Data
No full textDataset supporting:
Waters, J. M. et. al. (2019). Resolving Anomalies in the Critical Exponents of FePt Using Finite-Size Scaling in Magnetic Fields. Physical Review Applied.
Results of Monte Carlo simulations of FePt grains. Files are in HDF5 format with tables containing the raw data. Zero field and field data is included, with grain radii at 2.1nm, 3nm and 3.9nm.</span
Finite-size scaling of complex magnetic materials near the phase transition
No full textNano-technologies such as heat-assisted magnetic recording, magnetic particle hyperthermia and skyrmion racetrack memory have been developing rapidly in recent years. However, there have been a number of issues relating to the finite-size of materials relevant to prospective nano-technologies. FePt is the leading candidate material in the development of heat-assisted magnetic recording. In recent years, there have been conflicting reports of the phase transition behaviour and critical exponents of FePt which have been attributed to its complex, long-ranged internal interactions. This thesis identifies anisotropy as the cause of the inconsistent measurements of the critical exponents, and introduces a two-dimensional finite-size scaling framework which is capable of overcoming the anisotropic interactions of FePt. Using this new technique, the critical exponents of FePt are shown to be those of the Heisenberg model. Granular technologies, such as heat-assisted magnetic recording and magnetic particle hyperthermia, have been shown to have a distribution of Curie temperatures. Identifying the Curie temperature distribution is an important step in accelerating the development of granular technologies which operate across the magnetic phase transition. This thesis presents a new characterisation technique which can be used to identify the parameters of the Curie temperature distribution. This technique only requires measurements of the temperature dependent magnetisation, realisable from standard magnetometry. Other materials, such as MnSi and FeGe, are being targeted towards applications such as skyrmion racetrack memory. The internal magnetisation of these helimagnetic materials has a tendency to twist, forming complex topological structures known as skyrmions. The finite-size effects of such materials is little understood and work is needed to quantify them. This thesis presents a qualitative exploration of the finite-size effects of helimagnetic materials. We demonstrate that both finite-size and choice of experimental protocol can significantly impact on the extent of the skyrmion phase. This thesis also identifies the critical exponents of the Dzyaloshinskii-Moriya interaction by using finitesize scaling. This is a key step towards proper finite-size scaling of general helimagnetic materials in the future
Resolving anomalies in the critical exponents of <b>FePt</b> using finite-size scaling in magnetic fields
No full textFePt is the primary material being considered for the development of information storage technologies based on heat-assisted magnetic recording (HAMR). A practical realization of HAMR requires understanding the high-temperature phase transition behavior of FePt, including critical exponents and Curie temperature distributions as the fundamental HAMR media design characteristics. The studies so far found a significant degree of variability in the values of critical exponents of FePt and remain controversial. Here, we show that at the heart of this variability is the phase transition crossover phenomenon induced by two-ion anisotropy of FePt. Through Monte Carlo simulations based on a realistic FePt effective Hamiltonian, we demonstrate that in order to identify the critical exponents accurately, it is necessary to base the analysis on field-dependent magnetization data. We have developed a two-variable finite-size scaling method that accounts for the field effect. Through the use of this method, we show unambiguously that true critical exponents of FePt are fully consistent with the three-dimensional Heisenberg universality class
Parameterised Spin Model For FePt
No full textDataset supporting: Waters, J. M. et. al. (2019). Resolving Anomalies in the Critical Exponents of FePt Using Finite-Size Scaling in Magnetic Fields. Physical Review Applied. DOI:10.1103/PhysRevApplied.11.024028
Interaction strengths between Fe atoms in a parameterised spin model of FePt in the L10 crystal structure.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Identification of Curie temperature distributions in magnetic particulate systems
No full textThis paper develops a methodology for extracting the Curie temperature distribution from magnetisation versus temperature measurements which are realizable by standard laboratory magnetometry. The method is integral in nature, robust against various sources of measurement noise, and can be adopted to a wide range of granular magnetic materials and magnetic particle systems. The validity and practicality of the method is demonstrated using large-scale Monte–Carlo simulations of an Ising-like model as a proof of concept, and general conclusions are drawn about its applicability to different classes of systems and experimental conditions
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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