EuPtP is known to exhibit two valence ordering transitions, one at T 1 = 235 K and the other at T 2 = 190 K. For T > T 1, the Eu ions are in the valence fluctuating state. For T 2 < T < T 1, the Eu valence state is ordered along the c-axis with the sequence of Eu2+-Eu2+-Eu3+-Eu2+-Eu2+-Eu3+. Moreover, the stacking is replaced by another sequence of Eu2+-Eu3+-Eu2+-Eu3+ at temperatures below T 2. The substitution of As for P expands the lattice and decreases both T 1 and T 2. In this paper, we report the magnetic susceptibility and electrical resistivity of EuPtP1-xAsx single crystals. We observed two valence ordering transitions for 0 ≤ x ≤ 0.4, while a single valence ordering transition was detected for 0.55 ≤ x ≤ 0.6. No valence ordering transitions were observed for x = 0.7 down to the lowest temperature. Based on the experimental results, we present the phase diagram of EuPtP1-xAsx and discuss the Eu valence state in this system.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)