Peculiarities of the electronic transport in half-metallic Co-based Heusler alloys

Abstract

Electrical, magnetic and galvanomagnetic properties of half-metallic Heusler alloys of Co2YZ (Y = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn, Sb) were studied in the temperature range 4.2-900 K and in magnetic fields of up to 100 kOe. It was found that varying Y in Co2YZ alloys affects strongly the electric resistivity and its temperature dependence ρ(T), while this effect is not observed upon changing Z. When Y is varied, extrema (maximum or minimum) are observed in ρ(T) near the Curie temperature TC. At T ≤ TC, the ρ(T) behavior can be ascribed to a change in electronic energy spectrum near the Fermi level. The coefficients of normal and anomalous Hall effect were determined. It was shown that the latter coefficient, RS, is related to the residual resistivity ρ0 by a power law RS ~ ρ0 k /MS with MS the spontaneous magnetization. The exponent k was found to be 1.8 for Co2FeZ alloys, which is typical for asymmetric scattering mechanisms, and 2.9 for Co2YAl alloys, which indicates an additional contribution to the anomalous Hall effect. The type of the temperature dependence ρ(T) is analyzed and discussed in the frame of two-magnon scattering theory.

Half-Metallic Ferromagnets and Spin Gapless Semiconductors

“…To clarify the situation, precision investigations of the field and temperature dependences of the resistivity were carried out in [18] for Co 2 MeZ (Me = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn, Sb). Fig.…”

Magnetic and thermal properties of alloys close in composition to the spin gapless semiconductor Mn2CoAl

“…1 and 2 and references therein). The Heusler compounds family has more than 1500 alloys which exhibit various functional properties, i.e., magnetocaloric effect, 3,4 unusual thermal, 5,6 thermoelectric 7 and semiconductor [8][9][10] characteristics, properties of half-metallic ferromagnets 11,12,18 and spin gapless semiconductors. 13,14,19 The so-called full and inverse Heusler alloys are studied the most.…”

Peculiarities of Electronic Transport and Magnetic State in Half-Metallic Ferromagnetic and Spin Gapless Semiconducting Heusler Alloys

“…Thus, the purpose of the present work is a brief survey and analysis of the papers on the electron transport and magnetic characteristics of X 2 YZ alloys (X = Mn, Fe, Co; Y = Ti, V, Cr, Mn, Fe, Co, Ni; Z = Al, Si, Ga, Ge, In, Sn, Sb) and the establishment of the basic laws of their behavior when varying the Y-and Z-components. EXPERIMENTAL Synthesis of polycrystalline alloys and their heat treatment are described in detail in [14][15][16]. Elemental analysis was carried out by using a scanning electron microscope equipped with an EDAX X-ray microanalysis attachment.…”