Gigantic directional asymmetry of luminescence in multiferroic CuB2O4

TL;DR

This study reveals a significant directional asymmetry in luminescence in multiferroic CuB2O4, with a 70% change in intensity upon reversing magnetic field, enabling magnetic domain imaging.

Contribution

It demonstrates a large, controllable luminescence asymmetry in CuB2O4, surpassing previous observations, and introduces a method for imaging magnetic domains using this effect.

Findings

Luminescence intensity varies by about 70% with magnetic field reversal.

The asymmetry is due to interference between electric and magnetic dipole transitions.

Large directional luminescence asymmetry enables magnetic domain imaging.

Abstract

We report direction dependent luminescence (DDL), i.e., the asymmetry in the luminescence intensity between the opposite directions of the emission, in multiferroic CuB2O4. Although it is well known that the optical constants can change with the reversal of the propagation direction of light in multiferroic materials, the largest asymmetry in the luminescence intensity was 0.5 % so far. We have performed a measurement of photoluminescence with a He-Ne laser irradiation (633 nm). The luminescence intensity changes by about 70 % with the reversal of the magnetic field due to the interference between the electric dipole and magnetic dipole transitions. We also demonstrate the imaging of the canted antiferromagnetic domain structure of (Cu,Ni)B2O4 by using the large DDL.