Minimal model for the magnetic phase diagram of CeTi1-xScx Ge, GdFe1-xCox Si, and related materials
Abstract
We present a theoretical analysis of the magnetic phase diagram of CeTi1-x Scx Ge and GdFe1-x Cox Si as a function of the temperature and the Sc and Co concentration x, respectively. CeScGe and GdCoSi, as many other RTX (R = rare earth, T = transition metal, X = p-block element) compounds, present a tetragonal crystal structure where bilayers of R are separated by layers of T and X. While GdFeSi and CeTi0.75 Sc0.25 Ge are ferromagnetic, CeScGe and GdCoSi order antiferromagnetically with the R 4 f magnetic moments on the same bilayer aligned ferromagnetically and magnetic moments in nearest neighbouring bilayers aligned antiferromagnetically. The antiferromagnetic transition temperature TN decreases with decreasing concentration x in both compounds and for low enough values of x the compounds show a ferromagnetic behavior. Based on these observations we construct a simplified model Hamiltonian that we solve numerically for the specific heat and the magnetization. We find a good qualitative agreement between the model and the experimental data. Our results show that the main magnetic effect of the Sc → Ti and Co → Fe substitution in these compounds is consistent with a change in the sign of the exchange coupling between magnetic moments in neighbouring bilayers. We expect a similar phenomenology for other magnetic RTX compounds with the same type of crystal structure.
- Publication:
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Journal of Magnetism and Magnetic Materials
- Pub Date:
- June 2020
- DOI:
- 10.1016/j.jmmm.2020.166614
- arXiv:
- arXiv:1911.06235
- Bibcode:
- 2020JMMM..50366614C
- Keywords:
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- Magnetism;
- RTX;
- Condensed Matter - Materials Science;
- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- 13 pages, 4 figures