Tuning Magnetic and Structural
Transitions through
Valence Electron Concentration in the Giant Magnetocaloric Gd<sub>5–<i>x</i></sub>Eu<sub><i>x</i></sub>Ge<sub>4</sub> Phases
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Abstract
Valence electron concentration is a viable chemical tool
to control
the crystal structure and magnetism of Gd<sub>5</sub>Ge<sub>4</sub>. A decrease in the valence electron concentration achieved through
the substitution of Eu<sup>2+</sup> for Gd<sup>3+</sup> leads to the
formation of the interslab Ge–Ge dimers, phase transitions
to the Gd<sub>5</sub>Si<sub>2</sub>Ge<sub>2</sub>- and Gd<sub>5</sub>Si<sub>4</sub>-type structures, and a ferromagnetic ordering in the
Gd<sub>5–<i>x</i></sub>Eu<sub><i>x</i></sub>Ge<sub>4</sub> system. Gd<sub>4.75</sub>Eu<sub>0.25</sub>Ge<sub>4</sub> and Gd<sub>4.50</sub>Eu<sub>0.50</sub>Ge<sub>4</sub> undergo temperature-induced
magnetostructural transformations accompanied by giant magnetocaloric
effects
