Importance of doping and frustration in itinerant Fe-doped Cr2Al

We have performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a Neel temperature of 670 K. with known results on Fe-doping of anti-ferromagnetic bcc Cr. (Cr1-xFx)(2)Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing T-N to approximate to 170 K for x = 0.10. Antiferromagnetic behavior disappears entirely at x approximate to 0.125 after which point increasing paramagnetic behavior is exhibited. This is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which T-N gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explain that the Cr2Al-Fe suppression of magnetic order originates from two causes: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al. (C) 2015 Elsevier B.V. All rights reserved.