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Projects / Programmes source: ARIS

Influence of the electronic structure of materials on the magnetocaloric effect

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Research activity

Code Science Field Subfield
2.04.02  Engineering sciences and technologies  Materials science and technology  Metallic materials 

Code Science Field
P260  Natural sciences and mathematics  Condensed matter: electronic structure, electrical, magnetic and optical properties, supraconductors, magnetic resonance, relaxation, spectroscopy 
Keywords
magnetocaloric effect, magnetic entropy, exchange coupling, density-functional theory
Evaluation (rules)
source: COBISS
Evaluation of bibliographic research performance indicators according to ARIS methodology
Citations Citations for bibliographic records in COBIB.SI that are linked to records in citation databases
source: WoS source: Scopus source: COBISS
Researchers (4)
no. Code Name and surname Research area Role Period No. of publications
1.  15654  PhD Matej Andrej Komelj  Materials science and technology  Head  2007 - 2009  176 
2.  18594  PhD Paul John Mc Guiness  Materials science and technology  Researcher  2007 - 2009  338 
3.  24982  PhD Benjamin Podmiljšak  Materials science and technology  Technical associate  2007 - 2009  95 
4.  15597  PhD Zoran Samardžija  Materials science and technology  Researcher  2007 - 2009  577 
Organisations (1)
no. Code Research organisation City Registration number No. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  90,753 
Abstract
The magnetocaloric effect is characterised by an adiabatic change in the temperature or an isothermal change in the entropy of a material due to a variation in the external magnetic field. The phenomenon can be applied for magnetic refrigeration. The microscopic origin of the effect will be investigated on the basis of the electronic structure, obtained within the framework of the density-functional theory. The characteristic temperature and entropy changes will be determined by using the mean-field approximation and the Monte-Carlo method from the parameters calculated ab initio. We will interpret the influence of the electronic structure on the magnetocaloric effect, which will open up a possibility for the bottom-up tailoring of novel materials.
Significance for science
Investigations of alternative ways of cooling are important from the ecological and technological aspects, as well as they contribute new achievements in physics, chemistry, materials science, energetics, and others. Technologically promising and interesting is the magneto-caloric effect. This technology is not based on the application of the health and environment damaging gases, it does not contain complicated mechanical devices, and it is energetically efficient. It combines magnetic and structural phase transitions, hence it is related to magnetic and thermal properties, which makes it important for the development of the corresponding scientific fields. Of the key importance is the application of an efficient material, distinguished by a huge adiabatic temperature difference due to the change in the external magnetic field. An ideal material, which would exhibit a significant effect at the room temperature (or at the desired working temperature of the cooling device), does not exist yet, therefore an effort should be put in its development. A development of any new material or an improvement of existing materials is based either on finding completely new alloys in terms of chemical composition and crystal structure and on slight modifications of them, or it is about improving the phase composition, morphology, microstructure, purity, and other properties that are not directly related to the electronic structure but rather to the processing conditions and techniques. Within the projects: "Influence of the electronic structure of materials on the magneto-caloric effect" we mainly modeled material properties directly influenced by the electronic structure, whereas other aspects were mainly taken as ideal (single-phase composition, perfect chemical and crystal structure etc.). The results definitely demonstrated that some measured macroscopic properties at least to some extent originated from the complicated electronic structure , which most clearly followed from the calculated complex fermi surfaces, and from the comparisons between the theoretical and available experimental results. A complete qualitative agreement between theory and experiment was achieved in most cases, whereas a partial quantitative disagreement could be ascribe to the chemical disorder, the presence of impurities, morphology, microstructur, and other properties which were neglected. The future investigations should be therefore focused on searching for the materials with the appropriate intrinsic properties, and on the small modifications of them via the electronic structure, for example, by introducing light interstitial elements, like hydrogen, nitrogen or even carbon, which all retain the parent crystal structure and morphology. Very promising are the complex-metallic alloys with their unusual properties, therefore the upcoming investigations may be in this direction.
Significance for the country
The results of the research project: "Influence of the electronic structure of materials on the magnetocaloric effect" are important for the reputation of Slovenia in scientific community because the names of Slovene institutions and authors appear on relevant scientific publications and talks on international conferences. Besides, the topic of the project was the magnetocaloric effect, which is interesting from the point of view of ecology and economy, because its application may lead to the replacement of the old cooling technique by a new one. The Slovene industry, with a long tradition in refrigerator manufacturing, in the past expressed interest in magnetic cooling, and it is hoped that it will rely upon the domestic knowledge.
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