Determination of the infrared complex magneto-conductivity tensor in itinerant ferromagnets from Faraday and Kerr measurements

TL;DR

This paper introduces a method to determine the full complex magneto-conductivity tensor of itinerant ferromagnets using mid-infrared Faraday and Kerr measurements, avoiding absolute transmittance or reflectance data.

Contribution

It develops a technique to extract complex conductivity tensors from polarization measurements without needing absolute transmittance or reflectance data.

Findings

The method accurately determines sigma_xx and sigma_xy from Faraday and Kerr angles.

Results are validated against conventional transmittance, reflectance, and Kramers-Kronig analysis.

The approach is demonstrated on Ga_(1-x)Mn_xAs and SrRuO_3 films.

Abstract

We present measurement and analysis techniques that allow the complete complex magneto-conductivity tensor to be determined from mid-infrared (11-1.6 micron; 100-800 meV) measurements of the complex Faraday (theta_F) and Kerr (theta_K) angles. Since this approach involves measurement of the geometry (orientation axis and ellipticity of the polarization) of transmitted and reflected light, no absolute transmittance or reflectance measurements are required. Thick film transmission and reflection equations are used to convert the complex theta_F and theta_K into the complex longitudinal conductivity sigma_xx and the complex transverse (Hall) conductivity sigma_xy. theta_F and theta_K are measured in a Ga_(1-x)Mn_xAs and SrRuO_3 films. The resulting sigma_xx is compared to the values obtained from conventional transmittance and reflectance measurements, as well as the results from Kramers-Kronig analysis of reflectance measurements on similar films.