High frequency dielectric and magnetic anomaly at the phase transition in NaV2O5

TL;DR

This study reports high-frequency dielectric and magnetic anomalies at the phase transition in NaV2O5, linked to charge ordering and spin-charge coupling, observed through microwave and infrared measurements.

Contribution

It provides new insights into the dielectric and magnetic anomalies at T_c in NaV2O5, highlighting the role of charge ordering and spin-charge interactions.

Findings

Dielectric constants epsilon_a and epsilon_c decrease below T_c.

Anomalies correlate with charge ordering and spin-gap opening.

Microwave magnetic losses suggest coupling between spin and charge.

Abstract

We found anomalies in the temperature dependence of the dielectric and the magnetic susceptibiliy of NaV_2O_5 in the microwave and far infrared frequency ranges. The anomalies occur at the phase transition temperature T_c, at which the spin gap opens. The real parts of the dielectric constants epsilon_a and epsilon_c decrease below T_c. The decrease of epsilon_a (except for the narrow region close to T_c) is proportional to the intensity of the x-ray reflection appearing at T_c. The dielectric constant anomaly can be explained by the zigzag charge ordering in the ab-plane appearing below T_c. The anomaly of the microwave magnetic losses is probably related to the coupling between the spin and charge degrees of freedom in vanadium ladders.