Variable range hopping conductivity and spin glass behavior in spin-ladder Ba0.6K0.4Fe2Se3 single crystals

Area of Science:

• Condensed Matter Physics
• Materials Science
• Magnetism

Background:

• Barium-potassium-iron-selenide (Ba0.6K0.4Fe2Se3 or BKFS) is a material with potential magnetic properties.
• Understanding the interplay between crystal structure and magnetic behavior is crucial for developing new materials.

Purpose of the Study:

• To investigate the physical properties of Ba0.6K0.4Fe2Se3 (BKFS) single crystals.
• To determine the magnetic ground state and understand the magnetic interactions within BKFS.

Main Methods:

• Powder X-ray diffraction to analyze crystal structure and iron displacements.
• Temperature-dependent resistivity measurements to study electrical transport properties.
• Anisotropic DC magnetization, AC magnetic susceptibility, and specific heat measurements to probe magnetic behavior.

Main Results:

• X-ray diffraction revealed staggered iron displacements with varying Fe-Fe bond lengths.
• Resistivity data indicated variable range hopping behavior at low temperatures.
• Magnetic susceptibility measurements showed a cusp around 20 K, indicative of spin glass behavior, further supported by frequency-dependent AC susceptibility.
• Anisotropic susceptibility suggested an anisotropic Heisenberg-like spin glass with easy magnetization perpendicular to the chain direction.
• Specific heat measurements confirmed an insulating and spin glass ground state.
• Effective magnetic moments were reduced and close to spin-only magnetism with S=1/2.

Conclusions:

• Ba0.6K0.4Fe2Se3 (BKFS) exhibits an insulating spin glass ground state.
• The material displays characteristics of an anisotropic Heisenberg-like spin glass.
• The findings contribute to the understanding of magnetic phenomena in iron selenide compounds.