Hydrostatic pressure effects on the static magnetism in Eu(Fe_0.925Co_0.075)₂As₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism and Superconductivity

Background:

• EuFe$_{2}$As$_{2}$-based iron pnictides exhibit dual magnetic sublattices.
• These materials are tunable to superconductivity via chemical doping or pressure.
• Understanding pressure effects on magnetism is key to tuning properties.

Purpose of the Study:

• Investigate the impact of hydrostatic pressure on static magnetism in Eu(Fe$_{0.925}$Co$_{0.075}$)$_{2}$As$_{2}$.
• Establish a pressure-temperature (P-T) phase diagram for this compound.
• Explore the interplay between magnetism and pressure-induced superconductivity.

Main Methods:

• Electrical resistivity measurements.
• AC magnetic susceptibility analysis.
• Single-crystal neutron diffraction studies.

Main Results:

• The structural phase transition and Fe sublattice spin-density-wave order are suppressed by pressure, vanishing above 2.0 GPa.
• The Eu magnetic sublattice order persists up to 14 GPa, showing non-monotonic pressure dependence.
• Eu's magnetic state transitions from canted antiferromagnetic to ferromagnetic, then to an 'unconfirmed' antiferromagnetic structure with increasing pressure.
• Strong ferromagnetism of Eu coexists with pressure-induced superconductivity around 2 GPa.

Conclusions:

• Hydrostatic pressure significantly alters the magnetic landscape of Eu(Fe$_{0.925}$Co$_{0.075}$)$_{2}$As$_{2}$.
• A detailed P-T phase diagram reveals distinct magnetic phases and the suppression of Fe sublattice order.
• The coexistence of Eu ferromagnetism and superconductivity highlights complex electronic interactions in these pnictides.