Effect of a magnetic field on the long-range magnetic order in insulating Nd2CuO4, nonsuperconducting and superconducting Nd1.85Ce0.15CuO4

TL;DR

This study investigates how a magnetic field affects the magnetic order in insulating, nonsuperconducting, and superconducting Nd-based cuprates, revealing different responses linked to their structural and impurity phases.

Contribution

It provides new insights into the magnetic field effects on the magnetic order in Nd2CuO4 and Nd1.85Ce0.15CuO4, highlighting differences between non-superconducting and superconducting states.

Findings

Magnetic field induces canting in all Nd2CuO4 phases without changing spin structures.

Superconducting Nd1.85Ce0.15CuO4 exhibits a field-induced long-range AF order.

Impurity phases and lattice distortions are characterized and distinguished from magnetic effects.

Abstract

We have measured the effect of a c-axis aligned magnetic field on the long-range magnetic order of insulating Nd2CuO4, as-grown nonsuperconducting and superconducting Nd1.85Ce0.15CuO4. On cooling from room temperature, Nd2CuO4 goes through a series of antiferromagnetic (AF) phase transitions with different noncollinear spin structures. In all phases of Nd2CuO4, we find that the applied c-axis field induces a canting of the AF order but does not alter the basic zero-field noncollinear spin structures. Similar behavior is also found in as-grown nonsuperconducting Nd1.85Ce0.15CuO4. These results contrast dramatically with those of superconducting Nd1.85Ce0.15CuO4, where a c-axis aligned magnetic field induces a static, anomalously conducting, long-range ordered AF state. We confirm that the annealing process necessary to make superconducting Nd1.85Ce0.15CuO4 also induces epitaxial, three-dimensional long-range ordered cubic (Nd,Ce)2O3 as an impurity phase. In addition, the annealing process makes a series of quasi two-dimensional superlattice reflections associated with lattice distortions of Nd1.85Ce0.15CuO4 in the CuO2 plane. While the application of a magnetic field will induce a net moment in the impurity phase, we determine its magnitude and eliminate this as a possibility for the observed magnetic field-induced effect in superconducting Nd1.85Ce0.15CuO4.