Pressure dependence of antiferromagnetic and superconducting phases in U2Rh1−xPtxC2

Abstract

We report temperature (T)- and pressure (P)-dependent resistivity measurements on the isostructural compounds U2Rh1−xPtxC2 (x=0, 0.5, and 0.9) from which we construct a T−P−x phase diagram. Compounds with x=0 and x=0.5 are antiferromagnets below 22.1 and 9.4 K, respectively, and their Néel temperature (TN) decreases under applied pressure. For x=0, the critical pressure Pc required to suppress TN to zero temperature is projected to be about 8.8 GPa, but Pc for x=0.5 is between 1.6 and 2.1 GPa. At atmospheric pressure, increasing Pt concentration in U2Rh(1−x)PtxC2 tunes magnetic transition temperatures to zero at a critical value of xc≈0.7, and, consequently, we surmise the existence of a quantum-phase boundary in the P−x plane at T=0 K that extends from (P=0, x=xc) to (Pc≈8.8GPa, x=0). For x=0.9, superconductivity appears at Tc=1.09K, which decreases at a rate of ≈−1K/GPa that is nearly twice that found for U2PtC2 whose Tc is 1.47 K. Together, these results indicate that domes of magnetism and superconductivity formed with T−P−x variations are detached and that the two broken symmetries are independent of each other. Fluctuations in average composition produce rare regions that play an important role in determining physical properties of materials with noninteger x.

Source-reported materials — not catalogue approval

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