Magnetic Order and Other Phase Transitions in Mixed-Valent YbPd

Specific heat, thermal expansion, and electrical resistivity show that YbPd undergoes four phase transitions at 0.5, 1.9, 105, and 125 K. From magnetic-susceptibility measurements the transition at 0.5 K is found to be magnetic. The quasielastic magnetic linewidth is large as usual for mixed valence, but decreases with temperature and is smaller than kBT everywhere. The magnetic order of YbPd occurs at a fractional Yb valence of $v=2.8$ (measured by LIII absorption), i.e., near configurational crossover of 4f¹³ and 4f¹⁴.