Influence of symmetry on Sm magnetism studied on SmIr(2)Si(2) polymorphs

Polycrystalline samples of SmIr(2)Si(2) formed at room temperature both the low temperature phase (LTP) and the metastable high temperature phase (HTP), respectively, depending on the heat treatment. The samples were studied by X-ray powder diffraction, DTA, specific-heat and magnetization measureme...

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Bibliographic Details
Published in:Journal of alloys and compounds 2013-10, Vol.574, p.459-466
Main Authors: Valiska, Michal, Pospisil, Jiri, Prokleska, Jan, Divis, Martin, Rudajevova, Alexandra, Turek, Ilja, Sechovsky, Vladimir
Format: Article
Language:English
Subjects:
Alloys
Ground state
Indication
Magnetism
Magnetization
Phase transformations
Stacking
Symmetry
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Summary:Polycrystalline samples of SmIr(2)Si(2) formed at room temperature both the low temperature phase (LTP) and the metastable high temperature phase (HTP), respectively, depending on the heat treatment. The samples were studied by X-ray powder diffraction, DTA, specific-heat and magnetization measurements with respect to temperature and magnetic field. The first order LTP reversible reaction HTP polymorphic phase transition has been determined showing the huge temperature hysteresis of 264 degree C caused by the high energy barrier due to the change of stacking of the Sm, Ir and Si basal plane sheets within the transition. Both polymorphs show indications of antiferromagnetic order at low temperatures. The considerably different magnetic phase transitions determined for the LTP and HTP confirm the strong influence of crystal structure symmetry on magnetism in the two polymorphs. The magnetism in SmIr(2)Si(2) exhibits typical features caused by the specific behavior of Sm(3+) ion characterized by energy nearness of the ground state and first excited state and crystal field influence. The interpretation of experimental results is corroborated by results of ab initio electronic structure calculations.
ISSN:0925-8388