Order parameter segregation in Ce0.7La0.3B6: 4f octopole and 5d dipole magnetic order

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Cerium hexaboride (CeB6) exhibits complex thermophysical properties.
• Doping CeB6 with Lanthanum (La) induces an exotic ground state known as phase IV.
• Understanding the order parameter symmetries in phase IV is crucial for characterizing its exotic behavior.

Purpose of the Study:

• To investigate the order parameter symmetries in phase IV of Ce0.7La0.3B6.
• To elucidate the nature of the magnetic ordering below the phase IV transition temperature (T(IV) = 1.5 K).
• To explore the coexistence and interplay of different magnetic orders in this system.

Main Methods:

• Resonant x-ray scattering experiments were performed on Ce0.7La0.3B6.
• Analysis focused on the symmetries of the order parameters in phase IV.
• Temperature dependence and spatial correlations of the ordered phases were examined.

Main Results:

• Mesoscopic 5d dipole antiferromagnetic order with propagation vector Q0=(1/2 1/2 1/2) was observed both above and below T(IV).
• Below T(IV), this 5d order coexists with long-range 4f antiferro-octupole (AFO) order, also at Q0.
• Differences in temperature dependence and spatial correlation suggest order parameter segregation at low temperatures.

Conclusions:

• Phase IV of Ce0.7La0.3B6 is characterized by a complex interplay of 5d dipole antiferromagnetic and 4f antiferro-octupole orders.
• Order parameter segregation is proposed as a key feature of the low-temperature state.
• A simple model for AFO order is presented, consistent with experimental observations.