Ga Substitution Effect On The Valence Transition Of Eu2pt6al15

We have synthesized polycrystalline samples of Eu2Pt6(Al1-xGax)(15 )(x = 0, 0.05. 0.1, 0.2, 0.3, and 1) and examined electrical resistivity, magnetic susceptibility, high-field magnetization, and X-ray absorption spectra at the Eu L-3-edge. With increasing x up to 0.1, the first-order valence transition is shifted to low temperatures. For x >= 0.1. a nearly divalent state is stabilized down to the lowest temperature, and an antiferromagnetic order emerges below T-N = 13-16 K. For x = 0 and 0.05, magnetization curves in pulsed magnetic fields at T = 4.2 K clarify a field-induced valence transition at B-v= 29 and 19 T-v respectively. The ratio of B-v to the valence transition temperature is close to a universal value of other Eu-based systems with a different crystal structure (ThCr2Si2 type). The phase boundary curve in the T-B phase diagram is discussed thermodynamically.