Pressure dependence of the magnetic ground states in MnP

TL;DR

This study investigates how pressure influences the magnetic ground states of MnP, revealing suppression of certain magnetic orders and emergence of new phases, which may relate to its superconducting properties.

Contribution

The paper provides detailed neutron diffraction data on MnP's magnetic phases under pressure, highlighting the evolution and emergence of complex magnetic structures near the superconducting state.

Findings

Helical order disappears at ~1.2 GPa.

Ferromagnetic order appears at intermediate pressures.

Helical magnetic order re-emerges at 3.8 GPa.

Abstract

MnP, a superconductor under pressure, exhibits a ferromagnetic order below TC~290 K followed by a helical order with the spins lying in the ab plane and the helical rotation propagating along the c axis below Ts~50 K at ambient pressure. We performed single crystal neutron diffraction experiments to determine the magnetic ground states under pressure. Both TC and Ts are gradually suppressed with increasing pressure and the helical order disappears at ~1.2 GPa. At intermediate pressures of 1.8 and 2.0 GPa, the ferromagnetic order first develops and changes to a conical or two-phase (ferromagnetic and helical) structure with the propagation along the b axis below a characteristic temperature. At 3.8 GPa, a helical magnetic order appears below 208 K, which hosts the spins in the ac plane and the propagation along the b axis. The period of this b axis modulation is shorter than that at 1.8 GPa. Our results indicate that the magnetic phase in the vicinity of the superconducting phase may have a helical magnetic correlation along the b axis.