L2_1構造を持つCo_2CrGaフルホイスラー合金薄膜の作製とそれを用いた強磁性トンネル接合素子のトンネル磁気抵抗

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We have investigated that the structural and magnetic properties of Co_2CrGa full-Heusler alloy films and researched the tunnel magnetoresistance (TMR) in magnetic tunnel junctions (MTJs) using a Co_2CrGa electrode on a MgO(100) substrate. Co_2CrGa films were fabricated with substrate heating (RT&angeT_s&ange500℃) or post-annealing (RT&angeT_a&ange500℃) after the deposition using an ultrahigh vacuum dc magnetron sputtering system. L2_1-ordered Co_2CrGa thin films were obtained at T_s&range300℃ or T_a&range200℃. The maximum magnetic moment per formula unit measured at 5 K were 2.8μB and 2.6 μB for T_s and T_a=400℃, respectively, which are over 85% of the theoretical value. The maximum TMR of 18% at RT and 42% at 5 K are obtained for the MTJ using the L2_1-structured Co_2CrGa film as a bottom electrode. It is expected that the TMR can be enhanced by optimizing the interface of Co_2CrGa/AlOx.
2006-07-01