Physical Properties Of Several TI₂-Based Half-Metallic Materials

Solid-state electronics which is as one of the greatest creations in the 20th century, is on the base of controlling of electric field to modulate the transport of electrons and holes in the semiconductor. However, to our knowledge, the electron in the solid body is the carrier of charge and spin. Although the spin charater of the electron was discovered in 1920s, people have not exploitted spin character of electron in practical use. Along with the discoveries of giant magnetoresistance(GMR), colossal magnetoresistance(CMR) and tunneling magnetoresistance(TMR), people pay more and more attention on spin propertiy of electron, and develop a new subject—spintronics. The key of manufacture of spin device is to find a merely one spin direction or high spin polarization materials. Righ now, the half-metl with 100% polarization of electrons is coming insight. Theoretically, it has 100% spin polarization since the electrons at the Fermi level have only one spin direction. So it is one of classes of promising material for the future spintronic applications. Since the conception of half-metal was rised in the process of band structure calculations, predicting the half-metallic materials based on the theoretical calculations is always the main focus in this field.Using the first-principles calculations, we studied the electronic property and magnetic property of Ti₂ based Heusler alloy Ti₂NiZ(Z=Al,Ga,In) and Ti₂CoZ(Z= Si, Ge, Sn), and we found these tow series of alloys are all of half-metallic ferromagnet. The electronic property and magnetic property of Ti₂CoAl,Ti₂MnSb,Ti₂FeBi were also studied. Using the essential solid body bonding theory, among the possible ternary high crystal ordered Heusler alloys X2YZ, we gave the decision method of which structure to crystalizing between Cu₂MnAl and Hg₂CuTi shtrucure. When the atom radiou of X is the largest or the smallest among atoms X, Y and Z, the Cu₂MnAl structure is prefered; When the atom radious of X is in the middle of atoms X, Y and Z, the Hg₂CuTi structure is selected. The decision method is correct when applied to already synthetized ternary Heusler alloys Mn2NiGa, Ni₂MnGa, Ni₂FeGa and Cu₂MnAl, which reflects the rationality of our decision method. It is a convenience method for scientific researcher to estimate which high crystal structure to have in crystalizing process without the help of X ray diffraction, which can save time and material resource.Experimentally, we try to synthesize some half-metals by using the arc-melting method.