Magnetic and electrical properties of the half-metallic ferromagnets Co2CrAl

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

“…At the same time, the presence of atomic disorder results in an increase in both ρ ↑ and the total resistivity of the alloy as compared to the ideal case. As was shown in [3], the presence of a feature in the electronic spectrum of Co 2 CrAl half metallic fer romagnet under investigation is indicated by the effect of magnetic ordering on ρ. At temperatures below T C , we have (3) where the coefficient c > 0 [7].…”

“…As was shown in [3], the presence of a feature in the electronic spectrum of Co 2 CrAl half metallic fer romagnet under investigation is indicated by the effect of magnetic ordering on ρ. At temperatures below T C , we have (3) where the coefficient c > 0 [7]. Inclusion of the phonon contribution to the resistivity, which is described by the Bloch-Grüneisen function ρ ph (T), can explain the minimum of ρ(T) of Co 2 CrAl observed near T C (see Fig.…”

“…In [3,4], the specific behavior of ρ(T) in half metallic ferromagnets was attributed to both the scat tering mechanisms usually characterized by the relax ation time τ or the mean free path length l = 1/τ of conduction electrons and the specific electronic band structure of the alloys, i.e., the number n of charge car riers. Consequently, the conductivity σ = 1/ρ in the simplest case is determined by the well known relation (1) where e is the absolute value of the electron charge and m* is the effective mass of charge carriers.…”

“…Taking into account a rather high resistivity of half metallic ferromagnets, the total conductivity should be described by the expression (2) Naturally, the band gap contribution to the resistivity ρ ↓ is shunted at low σ, i.e., when σ ↑ ӷ σ ↓ . Conse quently, according to [3,4], the specific behavior of ρ(T) of half metallic ferromagnets is determined by the relation between the conductivities of two chan nels. When σ ↑ is low and comparable with σ ↓ , a con siderable role is played by the band gap contribution to the total resistivity.…”

“…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.…”