Correlation between Barrier Width, Barrier Height, and DC Bias Voltage Dependences on the Magnetoresistance Ratio in Ir–Mn Exchange Biased Single and Double Tunnel Junctions
Correlation between Barrier Width, Barrier Height, and DC Bias Voltage Dependences on the Magnetoresistance Ratio in Ir–Mn Exchange Biased Single and Double Tunnel Junctions
复制标题
Ir-Mn 交换偏置单隧道结和双隧道结中势垒宽度、势垒高度和直流偏置电压与磁阻比之间的相关性
DOI：
10.1143/jjap.39.l1035
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发表时间：
2000
影响因子：
1.5
通讯作者：
K. Inomata
中科院分区：
文献类型：
--
作者：
Y. Saito;M. Amano;K. Nakajima;Shigeki Takahashi;M. Sagoi;K. Inomata
采用超高真空溅射系统、传统光刻和离子束铣削制备了 Ir-Mn/CoFe/AlOx/Co90Fe10/AlOx/CoFe/Ir-Mn 的双自旋阀型双隧道结（DTJ）和 Ir-Mn/CoFe/AlOx/CoFe/Ni-Fe 的自旋阀型单隧道结（STJ）。通过改变沉积过程中的氧化条件和改变沉积后的退火温度，可以制备具有不同势垒高度的STJ，同时AlOx层厚度保持不变。势垒宽度、使用 Simmons 表达式估计的高度以及直流偏置电压对 MR 比的依赖性之间存在相关性。 VB 对隧道磁阻 (TMR) 比率的依赖性主要与势垒宽度有关，并且考虑到室温下通过势垒中的缺陷态进行自旋无关的两步隧道作为主要机制，TMR 比率随着偏置电压的增加而减小，这得到了很好的解释。在优化的氧化和退火条件下，低偏压下的最大TMR比以及TMR比减半(V1/2)时的直流偏压值在DTJ中分别为42.4%和952 mV，在STJ中分别为49.0%和425 mV。
Dual spin-valve-type double tunnel junctions (DTJs) of Ir–Mn/CoFe/AlOx/Co90Fe10/AlOx/CoFe/Ir–Mn and spin-valve-type single tunnel junctions (STJs) of Ir–Mn/CoFe/AlOx/CoFe/Ni–Fe were fabricated using an ultrahigh vacuum sputtering system, conventional photolithography and ion-beam milling. The STJs could be fabricated with various barrier heights by changing the oxidization conditions during deposition and changing the annealing temperature after deposition, while the AlOx layer thickness remained unchanged. There was a correlation between barrier width, height estimated using Simmons' expressions, and dc bias voltage dependence on the MR ratio. The VB dependence on the tunneling magnetoresistance (TMR) ratio was mainly related to the barrier width, and the decrease in the TMR ratio with increasing bias voltage is well explained, taking into account the spin-independent two-step tunneling via defect states in the barrier, as a main mechanism, at room temperature. Under optimized oxidization and annealing conditions, the maximum TMR ratio at a low bias voltage, and the dc bias voltage value at which the TMR ratio decreases in value by half (V1/2) were 42.4% and 952 mV in DTJs, and 49.0% and 425 mV in STJs, respectively.