# Improper multiferroicity and colossal dielectric constants in Bi$_{2}$CuO$_{4}$

## TL;DR

This study reveals that Bi$_{2}$CuO$_{4}$ is an improper multiferroic with colossal dielectric constants, showing complex magnetic and dielectric behaviors including short-range order and non-Debye relaxation.

## Contribution

It demonstrates the coexistence of multiferroicity and colossal dielectric constants in Bi$_{2}$CuO$_{4}$, highlighting its potential for multifunctional applications.

## Key findings

- Bi$_{2}$CuO$_{4}$ is an improper multiferroic with a ferroelectric state near magnetic transition.
- Presence of polar and magnetic short-range order above Neel temperature.
- Colossal dielectric constants with grain and grain boundary contributions exhibiting non-Debye relaxation.

## Abstract

The layered cuprate Bi$_{2}$CuO$_{4}$ is investigated using magnetic, dielectric and pyroelectric measurements. This system is observed to be an improper multiferroic, with a robust ferroelectric state being established near the magnetic transition. Magnetic and dielectric measurements indicate the presence of a region above the antiferromagnetic Neel temperature with concomitant polar and magnetic short range order. Bi$_{2}$CuO$_{4}$ is also seen to exhibit colossal dielectric constants at higher temperatures with clearly distinguishable grain and grain boundary contributions, both of which exhibit non-Debye relaxation.