Magnetic and anomalous electronic transport properties of the quaternary Heusler alloys Co_2Ti_(1-x)Fe_xGe

摘要

The half-metallic Heusler alloy Co_2TiGe has a ferromagnetic ground state with a low magnetic moment (2 μB). It is free of atomic antisite disorder but has low Curie temperature (~390 K). In contrast the other cobalt based Heusler alloy Co_2FeGe has high Curie temperature (~980 K) and high magnetic moment (5.6 μB) while exhibiting antisite disorder and lack of half-metallicity. Hence it is of interest to investigate the magnetic and transport properties of solid solutions of these two materials with contrasting char acteristics. We report the structural, magnetic and electronic transport properties of quaternary Co_2Ti_(1-x) Fe_xGe (x=0.2,0.4,0.6,0.8) Heusler alloys. The alloys crystallize in L2_1 structure but with antisite disorder. The magnetization measurements revealed that the alloys were of soft ferromagnetic type with high Curie temperatures. Deviation from Slater-Pauling behavior and drastic change in electronic transport properties with some anomalous features were observed.The complex electronic transport properties have been explained using different scattering mechanisms.