Examination of the critical behavior and magnetocaloric effect of the ferromagnetic Gd-Au-Si quasicrystal approximants

We investigate the critical behavior and magnetocaloric effects of the Gd-Au-Si (GAS) ferromagnetic qua-sicrystal approximants, Gd13.7Au72.7Si13.6 [referred to as GAS(0)] and Gd15.4Au68.6Si16.0 [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 similar to 30 K, which stems from a broad feature in the specific heat.