Atomic disorder and the magnetic, electrical, and optical properties of a Co2CrAl Heusler alloy

Specific features of the electrical resistance of half-metallic ferromagnetic alloys Co2CrAl and Co2CrGa

“…A difference in the behavior of the electrical and magnetic properties of the alloys under consider ation is that Co 2 CrGa basically exhibits disordering in the Cr and Ga sublattices, whereas such disordering in Co 2 CrAl takes place in all sublattices. Therefore, in our opinion, the alloys Co 2 CrGa is preferred for the use in spintronic devices.…”

“…The structural heter ogeneity of the samples was also associated in [5,6] with a difference-almost by a factor of 2-between the experimentally measured and calculated magnetic moments of the ultimately ordered Co 2 CrAl alloy. However, as was correctly mentioned in [2], the sign change of the resistance temperature coefficient near T C in the absence of structural changes in this temper Abstract-It has been shown by comparing the results of studying the electrical and magnetic properties of the half metallic ferromagnetic Heusler alloys Co 2 CrAl and Co 2 CrGa with the calculations of their elec tronic structure that high values of the electrical resistivity ρ are caused by a disordered distribution of atoms over the sites of the L2 1 cubic structure, and the anomalous behavior of ρ(T) is associated with the transfor mation of the electronic spectrum due to the ferromagnetic to paramagnetic transition. …”

“…As is known [1][2][3][4][5][6], the depth and width of the band gap of a half metallic ferromag net can vary considerably under the action of internal stress, structure distortions and especially as a result of disordering effects. As was shown in [2], a decrease in the magnitude of the magnetic moment of real Co 2 CrAl samples as compared to the calculated value for the ideal ordered alloy can be caused by the pres ence of Co atoms in the positions of Cr and Al. This naturally leads to a decrease in the depth of the band gap in the electronic spectrum and, consequently, to a decrease in ρ ↓ .…”

“…2, the residual resistivity of the Co 2 CrAl and Co 2 CrGa alloys is ρ 0 ~ 1.5 and 1.3 μΩ m, respectively. In addition, the ρ(T) curves of these half metallic fer romagnets near the Curie point T C are characterized by pronounced features: a sign change of the resis tance temperature coefficient of the Co 2 CrAl alloy [2,3] and a peak type anomaly in Co 2 CrGa [4]. The high values of ρ 0 and the negative resistance temperature coefficient of Co 2 CrAl at T < T C were attributed in [5,6] to the presence of a mixture of metallic and semi conductor phases in the samples.…”

“…Owing to this reason, studying the physical properties of half metallic ferromagnetic alloys as promising objects for possible use in spintronic devices has been recently of great interest. The energy gap in the half metallic fer romagnetic alloys Co 2 CrAl and Co 2 CrGa under inves tigation is known to be formed at the Fermi level in the subband of electrons with spins oriented opposite to the magnetization vector (see, e.g., [1][2][3][4][5][6] and refer ences therein). These alloys are ordered to form the crystal structure L2 1 of cubic symmetry.…”