Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 15: Magnetic Half-metals and Oxides I

MA 15.6: Vortrag

Mittwoch, 24. März 2010, 11:30–11:45, H22

A Fermi-level-tuned half-metallic Heusler compound: Co₂FeAl_0.5Si_0.5 — •Rong Shan^1,2, Hiroaki Sukegawa¹, Wenhong Wang¹, Koichiro Inomata¹, Benjamin Balke², Gerhard H. Fecher², and Claudia Felser² — ¹Magnetic Materials Center, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, 305-0047, Japan — ²Institute of Inorganic and Analytical Chemistry,Johannes Gutenberg - University, 55099 Mainz

Balke B. and Fecher G.H. et al. in our group made a theoretical prediction of Fermi level tuning in Heusler compounds, which suggested that the Fermi level of Co₂Mn_1−xFe_xSi and Co₂FeAl_1−xSi_x could be tuned to achieve the half-metallicity by the element substituting easily. However, to realize this prediction is a difficulty in experiment because of the perplexing relationship between the spin polarization of the quaternary Heusler compound and its structure disorder, resulting from the thermal treatment. Very recently, we confirmed Fermi level tuning in Heusler alloy Co₂FeAl_0.5Si_0.5 (CFAS). Half-metallic band gap of CFAS was proved even at room temperature by the behavior of differential conductance of CFAS/(MgAl₂)O_x/CoFe magnetic tunneling junctions with an unexplored crystalline (MgAl₂)O_x barrier. CFAS exhibits the highest effective spin polarization (P_eff) at 300 K and the weakest temperature dependence of P_eff among all known half-metals. Further study shows that P_eff of CFAS decays with increasing temperature (T) following T^3/2 law perfectly, which indicates that the depolarization of CFAS is determined by spin wave excitation only.