New analytical software developed.

The Numerical Algorithms Group (NAG) have announced that its numerical components have played an integral part in new analytical software developed by a Professor at the University of Oxford. The original impetus for developing the new analytical software application came from the availability of new experimental probes for studying magnetism. Neutron spectroscopy, in particular, has become a very powerful probe of the magnetic state of atoms thanks largely to advances in instrumentation at spallation neutron sources like the ISIS Facility at the Rutherford Appleton Laboratory. This technique makes it possible to obtain accurate measurements of level splittings in atoms caused by interactions with the crystalline environment. Detailed information on the many-electron states of atoms can be obtained from these level splittings and the corresponding spectral intensities.

Experiments that determine the electronic state of atoms in magnetic substances are extremely valuable for understanding the origin of magnetic behaviour and for engineering materials with new or improved magnetic properties. Armed with extensive experimental data, Professor Andrew Boothroyd, at the University of Oxford Physics Department, needed the analytical tools to work out the state of the electrons and hence understand their magnetic behaviour.

The creation of SPECTRE--the system designed to undertake the data analysis--and its subsequent evolution took place over many years as specific problems arose during the course of the research. SPECTRE uses the most up-to-date atomic models, which makes the results very accurate and quantitative. In brief, it calculates the neutron spectra in terms of a small number of unknown parameters, and determines these parameters by least-squares fitting to the data. The core of the calculation is a series of matrix diagonalizations carried out by NAG routines designed to handle Hermitian matrices. The least-squares fitting is also performed by NAG routines. The lowest energy eigenfunctions found by the program are used to calculate other experimentally accessible physical properties such as the magnetic susceptibility and specific heat capacity. SPECTRE will be made freely available to other magnetic materials groups in the hope that it will make it easier for scientists to interpret neutron spectroscopy data and thereby contribute towards the improvement of magnet materials.

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