Effect of disorder on various physical properties ofCo2CrAlHeusler alloy films: Experiment and theory

Electric and Magnetic Signatures of Structural and Chemical Ordering of Heusler Alloy Films

“…The films were amorphous or partially crystalline except the NiMn-Ga sputtered films in which XRD shows a single broad (220) peak typical of microcrystalline A2 structure of fully disordered HA structure. In as-deposited state the films were nonmagnetic or very weakly magnetic (Co 2 MnGa) and after ordering they revealed crystalline B2 or L2 1 [7,8] or tetragonal [2] structure and show ferromagnetic ordering. The resistivity measurements were carried in situ in a high-vacuum chamber used for flash-evaporation at temperature varying from 300 to 800 K with a scan rate of 4 K/min.…”

“…Films of Co 2 CrAl, Co 2 MnGa and off-stoichiometric Ni 2 Mn 1+x Sn 1−x (x = 0.4) were prepared by flash evaporation [7] from HA powders of proper composition onto liquid nitrogen cooled glass substrates. The off--stoichiometric Ni 2 Mn 1+x Ga 1−x (x = 0.15, 0.4) films were prepared by rf-sputtering at room temperature.…”

“…Epitaxial HA films prepared by molecular--beam epitaxy have been shown to grow pseudomorphically on GaAs substrates with L2 1 or B2 structures [3]. Frequently, however, HA films have been deposited by sputtering [4,5], laser ablation [6], or flash-evaporation [7] at room temperature (RT) with subsequent annealing. HA films deposited at RT or lower temperatures have, as a rule, highly disordered structure (amorphous or partially crystalline) [7] and chemical disorder significantly different from that of typical HA with L2 1 or B2 structure.…”

“…Frequently, however, HA films have been deposited by sputtering [4,5], laser ablation [6], or flash-evaporation [7] at room temperature (RT) with subsequent annealing. HA films deposited at RT or lower temperatures have, as a rule, highly disordered structure (amorphous or partially crystalline) [7] and chemical disorder significantly different from that of typical HA with L2 1 or B2 structure. In bulk HA ordering is typically achieved by annealing at temperatures as high as 1000-1300 K for many days, but in HA films such a procedure is obviously unacceptable.…”

Magnetic and electrical properties of the half-metallic ferromagnets Co2CrAl

“…In other words, in this alloy for spin down electrons at the Fermi level E F , there is an energy gap, which, according to differ ent authors [1,2,4,5], has a width of 0.2-0.5 eV. The Co 2 CrAl alloy in the ordered state stands out among the half metallic ferromagnets by the ultimate spin polarization of ~100%.…”