Crystalline structure and magnetic properties of Fe_2CrSi Heusler alloy films: New ferromagnetic material for high-performance magnetic random access memory

摘要

A new Heusler alloy, Fe_2CrSi, which has high spin polarization (P), low saturation magnetization (M_s), and a low Curie temperature (T_C), was investigated in order to fabricate high-performance magnetic tunnel junctions (MTJs) with a high tunnel magnetoresistance ratio and with low critical current for the spin-transfer switching method, or a low switching field for the thermally assisted magnetization reversal technique. The main results are as follows: (1) P and the magnetic moment of Fe_2CrSi with an L2_1 structure were 0.98 and 1.98 mu_B/f.u., respectively, according to density of states calculations. (2) Fe_2CrSi films show the (100) orientation with a B2 structure on a MgO substrate upon a thermal treatment with optimum temperature and duration. (3) Fe_2CrSi films have M_s and T_C values of 385 emu/cm~3 and 630 K, respectively. (4) The (100) oriented epitaxial MTJs are produced with Fe_2CrSi films fabricated with the optimized thermal treatment condition. It is found that the Fe_2CrSi Heusler alloy films are a suitable ferromagnetic material for high-performance magnetic random access memory.