Magnetic Properties of FeAs Single Crystal

Magnetic measurements have been performed on FeAs single crystals and polycrystalline samples. Magnetic measurements revealed a very sharp spin-glass magnetic transition in self flux grown single crystal. The bifurcation point between zero field cooled (ZFC) and field cooled (FC) magnetization occurs at 130 K. Susceptibility of flux grown single crystals revealed ferromagnetic-type behavior in the temperature range 4-300 K, while single crystals grown by iodine transport vapor were non-magnetic revealed features associated with antiferromagnetic and spin wave characteristics. The shift in Raman lines reveled sharper peaks for the crystals grown by vapor transport method than that obtained for the flux grown crystals. The difference in the spectrum may indicate sharper distribution in the bonding strength between Fe and As ions in crystals grown by the iodine vapor transport method.