کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1801575 | 1024572 | 2008 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Transitions involving conical magnetic phases in a model with bilinear and biquadratic interactions
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
فیزیک و نجوم
فیزیک ماده چگال
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چکیده انگلیسی
In a previous work a model was proposed for the phase transitions of crystals with localized magnetic moments which at low temperature have a “conical” arrangement that at higher T transforms into a more symmetrical structure (depending on the compound) before becoming totally disordered. The model assumes bilinear and biquadratic interactions between magnetic moments up to the fifth neighbours, and for any given T the structure with the least free energy is obtained by a mean-field approximation (MFA). The interaction constants are derived from ab initio energy calculations. In this work we improve upon that model modifying the MFA in such a way that a continuous (instead of discontinuous) spectrum of excited states is available to the system. In the previous work, which dealt with LaMn2Ge2 and LaMn2Si2, we found that transitions to different structures can be obtained for increasing T, in good qualitative agreement with experiment. The critical temperatures, however, were exaggeratedly high. With the new MFA we obtain essentially the same behaviour concerning the phase transitions, and critical temperatures much closer to the experimental ones.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Magnetism and Magnetic Materials - Volume 320, Issue 6, March 2008, Pages 851-856
Journal: Journal of Magnetism and Magnetic Materials - Volume 320, Issue 6, March 2008, Pages 851-856
نویسندگان
Vittorio Massidda,