Optical evidence for a spin-filter effect in the charge transport of $Eu_{0.6}Ca_{0.4}B_{6}$

TL;DR

This study uses optical reflectivity measurements to investigate the spin-filter effect in charge transport of Eu_{0.6}Ca_{0.4}B_{6}, revealing how magnetic field and temperature influence its optical and electronic properties.

Contribution

It provides new optical evidence for a spin-filter effect in Eu_{0.6}Ca_{0.4}B_{6} and details how magnetic field and temperature affect its plasma edge and conductivity.

Findings

Optical reflectivity shows increased slope at plasma edge with decreasing temperature and increasing magnetic field.

The plasma edge does not shift blue as in EuB_{6}, indicating different electronic behavior.

Optical data confirms exponential decrease of resistivity with increasing magnetization.

Abstract

We have measured the optical reflectivity $R(\omega)$ of $Eu_{0.6}Ca_{0.4}B_{6}$ as a function of temperature between 1.5 and 300 $K$ and in external magnetic fields up to 7 $T$. The slope at the onset of the plasma edge feature in $R(\omega)$ increases with decreasing temperature and increasing field but the plasma edge itself does not exhibit the remarkable blue shift that is observed in the binary compound $EuB_{6}$. The analysis of the magnetic field dependence of the low temperature optical conductivity spectrum confirms the previously observed exponential decrease of the electrical resistivity upon increasing, field-induced bulk magnetization at constant temperature. In addition, the individual exponential magnetization dependences of the plasma frequency and scattering rate are extracted from the optical data.