Scanning electron microscopy, energy dispersive x-ray spectroscopy, and depth profiling with Auger electron spectroscopy were used to characterize surface iron present on a ${\mathrm{CaB}}_6$ single crystal. The crystal was grown by the aluminum flux method and displayed ferromagnetism at 300 K. For similarly prepared samples, treatment with hydrochloric acid eliminated the ferromagnetism. In previous work it was speculated that the iron is deposited onto the ${\mathrm{CaB}}_6$ surface during flux removal. The Auger depth profiles presented here reveals that the iron is indeed concentrated in the surface region.

• Received 17 January 2003

DOI:https://doi.org/10.1103/PhysRevB.67.172410