Physical properties measurement system (ppms)

Heat capacity measurements were performed for mosaics of single crystals using the He3 option in a Quantum Design Physical Properties Measurement System for temperatures 400 mK<T<20 K. Magnetization M(T, H) measurements were carried out for mosaics of single crystals for temperatures T=1.8–350 K under an applied magnetic field of H=5 kOe applied parallel to the c-axis using a Quantum Design Magnetic Property Measurement System. Magnetic susceptibility χ is defined as the ratio M/H. Zero magnetic field electrical resistance R was measured using the He3 option in Quantum Design Physical Properties Measurement System for temperatures 400 mK<T<300 K. Several individual crystals were measured for each concentration, which revealed a high degree of batch uniformity. The angular dependence of the superconducting upper critical field was measured using the superconducting magnet (SCM-1) dilution refrigerator system at the National High Magnetic Field Laboratory for H<18 T and T=20 mK. Additional magnetoresistance measurements were performed at the National High Magnetic Field Laboratory, Tallahassee, up to magnetic fields of 35 T and at T=50 mK.

15 unit cell (~6 nm) NdNiO₃ films were grown by RF magnetron sputtering on NdGaO₃ and YAlO₃ substrates, in an Ar/O₂ gas mixture, with a 9 mTorr growth pressure, as described in detail elsewhere15 . Neither film is relaxed. The in-plane longitudinal resistivity was measured as a function of temperature in a Quantum Design Physical Properties Measurement System (PPMS). TEM cross-sections along [001]_O and [1 0]_O (the subscript indicates the orthorhombic orientation) were prepared using a focused ion beam with final milling energies of 5 kV Ga ions. High-angle, annular dark-field (HAADF)-STEM imaging and (LA-)PACBED experiments were conducted on a 300 kV FEI Titan S/TEM (C_s = 1.2 mm). A convergence semi-angle of 9.6 mrad was used for high resolution STEM imaging, while 9.6 and a reduced angle of 3.4 mrad was used for PACBED. LA-PACBED patterns are obtained from roughly a 12 × 12 unit cell area. An FEI double-tilt holder was used for room temperature PACBED and high resolution imaging, while a Gatan 636 double-tilt LN₂ holder was used for low temperature experiments. All cold-stage experiments were carried out a temperature of 105 K, which remained stable throughout the data acquisition. PACBED simulations were carried out using the Kirkland multislice code44 at 0 K.

Electrical resistivity and Seebeck effect were measured on properly shaped Cu₃As single crystals using the commercial apparatus Physical Properties Measurement System (PPMS, Quantum Design) with homemade sample holders. The electrical resistivity was measured in a standard four-probe configuration, experimentally realized with copper leads glued to the sample through silver paint, in a temperature range between 2 and 310 K and magnetic field up to 9 Tesla. In the Seebeck effect setup, one side of the sample was anchored to a thermal mass, while a resistive heater (R = 2.8 kΩ) was glued to the other side in order to generate a temperature gradient. A calibrated Chromel-Au-Chromel thermocouple was used to measure the temperature gradient across the sample, while two copper electrodes were attached to the sample to pick up the Seebeck voltage. The Seebeck data have been collected between 290 and 15 K.
Magnetic susceptibility was measured both on a single crystal and on a polycrystalline sample of Cu₃As using the commercial apparatus SQUID (MPMS, Quantum Design). The temperature-dependent magnetization measurements were acquired in external magnetic fields of 1 T, from 5 to 300 K.