Optical-spectroscopic detection of spin-exchange interaction pyrochlore molybdates

Area of Science:

• Condensed matter physics
• Materials science
• Magnetism

Background:

• Pyrochlore molybdates R2Mo2O7 display a transition from ferromagnetic metal to spin-glass insulator.
• This transition is influenced by the size of the R ion.

Purpose of the Study:

• To determine nearest-neighbor spin correlations in pyrochlore molybdates.
• To investigate the physical parameters governing the magnetic ground states.

Main Methods:

• Optical spectroscopy was employed to analyze spin correlations.
• The orbitally degenerate Hubbard model was used for theoretical analysis.

Main Results:

• Effective on-site Coulomb energy (Ueff) and Hund's coupling (JH) were estimated.
• The superexchange interaction between Mo ions was found to depend on the JH/Ueff ratio.

Conclusions:

• The JH/Ueff ratio dictates the phase boundary of magnetic ground states in these materials.
• Experimental and theoretical findings confirm the dependence of magnetic properties on electronic parameters.