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In this report, a successful thermodynamical model was employed to understand the structural transition in Er5Si4, able to explain the decoupling of the magnetic and structural transition. This was achieved by DFT calculations, which were used to determine the energy differences at 0 K, using a LSDA+U approximation. It was found that the M structure is the stable phase at low temperatures, as verified experimentally with a value of ΔF0=-0.262 eV. Finally, a variation of Seebeck coefficient (~6 μV) was determined at the structural transition, which allows to conclude that the electronic entropy variation is negligible in the transition. [ABSTRACT FROM AUTHOR]

Magnetic materials with strong spin-lattice coupling are a powerful set of candidates for multifunctional applications because of their multiferroic, magnetocaloric (MCE), magnetostrictive and magnetoresistive effects. In these materials there is a strong competition between two states (where a state comprises an atomic and an associated magnetic structure) that leads to the occurrence of phase transitions under subtle variations of external parameters, such as temperature, magnetic field and hydrostatic pressure. In this review a general method combining detailed magnetic measurements/analysis and first principles calculations with the purpose of estimating the phase transition temperature is presented with the help of two examples (Gd5Si2Ge2 and Tb5Si2Ge2). It is demonstrated that such method is an important tool for a deeper understanding of the (de)coupled nature of each phase transition in the materials belonging to the R5(Si,Ge)4 family and most possibly can be applied to other systems. The exotic Griffiths-like phase in the framework of the R5(SixGe1-x)4 compounds is reviewed and its generalization as a requisite for strong phase competitions systems that present large magneto-responsive properties is proposed. [ABSTRACT FROM AUTHOR]

In this report, a successful thermodynamical model was employed to understand the structural transition in Er5Si4, able to explain the decoupling of the magnetic and structural transition. This was achieved by DFT calculations, which were used to determine the energy differences at 0 K, using a LSDA+U approximation. It was found that the M structure is the stable phase at low temperatures, as verified experimentally with a value of ΔF0=-0.262 eV. Finally, a variation of Seebeck coefficient (~6 μV) was determined at the structural transition, which allows to conclude that the electronic entropy variation is negligible in the transition. [ABSTRACT FROM AUTHOR]