Examination of the critical behavior and magnetocaloric effect of the ferromagnetic Gd-Au-Si quasicrystal approximants
Takayuki Shiino, Girma Hailu Gebresenbut, Cesar Pay Gómez, Ulrich Häußermann, П. Нордблад, A. Rydh, R. Mathieu
Abstract
We investigate the critical behavior and magnetocaloric effects of the Gd-Au-Si (GAS) ferromagnetic quasicrystal approximants, ${\mathrm{Gd}}_{13.7}{\mathrm{Au}}_{72.7}{\mathrm{Si}}_{13.6}$ [referred to as GAS(0)] and ${\mathrm{Gd}}_{15.4}{\mathrm{Au}}_{68.6}{\mathrm{Si}}_{16.0}$ [GAS(100)]. The former is a conventional Tsai-type 1/1 approximant crystal, while the latter has a slightly different atomic decoration from the Tsai type (thus referred to as ``pseudo-Tsai'' type). Their critical exponents at the ferromagnetic transitions are close to those of the mean-field theory. Both GAS systems exhibit an interesting magnetic-field dependence of the specific heat, which is reflected in the behavior of their magnetocaloric effect (MCE). The MCE is characterized by an adiabatic cooling (heating) effect over a relatively broad temperature range below $\ensuremath{\sim}30$ K, which stems from a broad feature in the specific heat.