Effect of Fe substitution for Co on structure, electrical resistivity, and magnetic properties of Heusler type Co2-xFe1+xSi alloys

The effect of substitution of Fe for Co on structure, electrical resistivity, and magnetic properties of full Heusler type Co2-xFe1+xSi (0 <= x <= 1) alloys was investigated. The order-disorder transitions were studied by X-ray diffraction measurements followed by Rietveld refinement analysis as well as by Fe-57 Mossbauer spectroscopy. The results revealed that these alloys consist of mostly L2(1) ordered phase and some B2 disordered phase up to x < 0.25. However, for x >= 0.25, the alloys consisted of L2(1) ordered phase and DO3 disordered phase. The electrical resistivity behaviour with temperature showed two distinct regions. In region I, the resistivity exhibited two-magnon scattering mechanism (T-9/2 dependence) showing a signature of half-metallic ferromagnetism. However, in region II, the resistivity behaviour was governed by T-n power law and n value was found to vary from 2.98 to 1.38 with increasing Fe content. The room temperature magnetization studies confirmed the enhancement of the magnetic moment with increasing Fe substitution up to x = 0.5 in Co2-xFe1+xSi alloys. However, upon further increasing Fe content, the magnetic moment was found to decrease and this was explained in terms of localization effects originating mainly in the Co anti-site disorder. (C) 2013 AIP Publishing LLC.