We have investigated spin-dependent transport in magnetic tunnel junctions based on ferromagnetic oxides. Three types of junctions were fabricated from thin trilayer films that were grown on different substrates using both new and conventional growth techniques. Typical colossal magnetoresistance (CMR) oxide, La0.67Sr0.33MnO3 and 4d-based ferromagnetic oxide, SrRuO3 were explored as electrode materials. Magnetotransport on the junction systems was systematically conducted by varying device size and configuration, temperature, bias voltage, and direction of applied field. The transport properties were compared with previous reports and analyzed in parallel with microscopy study.; Off-axis sputtering, a relatively new method for the oxide growth enabled smoother surfaces and more uniform barrier interfaces in manganite homo-trilayers. We obtained highly symmetric and well-defined magnetoresistive behaviors for the manganite junctions. Large MR was achieved in a small magnetic field of about 80 Oe. For the first time in oxide junction systems, scaling has been finely done over junction areas and barrier thicknesses. Surprisingly, MR was sustained to near room temperature, representing the highest temperature ever reported in the manganite junction systems.; Ruthenate-incorporating junctions were tried for the first time. We found a small MR of 2.7% for a ruthenate homo-junction through a Tesla-range field scan. We also obtained an inverse MR of −16% for a manganite-ruthenate hetero-junction, corresponding to the negative spin polarization of −9% at EF for SrRuO3. The observation is the manifestation of the existence of a negatively polarized material at the Fermi level, and also a proof of the general applicability of Julliere model. However, the ruthenate-involving junctions showed worse barrier interface uniformity and potential interfacial compound formation. Therefore, poor area and barrier thickness scalings and heavy bias dependence of magnetotransport resulted from the junctions, particularly, ruthenate homo-junctions. These results on oxide-based junctions indicate that the interface uniformity is a critical factor for determining junction performance.
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机译：我们已经研究了基于铁磁氧化物的磁性隧道结中的自旋依赖性输运。三种类型的结由三层薄膜制成，这些薄膜使用新的和常规的生长技术在不同的基板上生长。典型的巨磁阻氧化物La 0.67 Sr 0.33 MnO 3 和4 基铁磁氧化物，探索了SrRuO 3 作为电极材料。通过改变器件的尺寸和配置，温度，偏置电压和施加磁场的方向，系统地进行了结系统上的磁传输。传输性能与以前的报告进行了比较，并与显微镜研究同时进行了分析。离轴溅射是一种相对较新的氧化物生长方法，可在锰矿均质三层膜中实现更光滑的表面和更均匀的势垒界面。我们获得了锰结的高度对称且定义明确的磁阻行为。在大约80 Oe的小磁场中实现了大MR。首次在氧化物结系统中，在结区域和势垒厚度上进行了精细缩放。出人意料的是，MR维持在接近室温，这是锰结系统中报道的最高温度。引入钌酸的连接是第一次尝试。通过特斯拉范围场扫描，我们发现钌酸同质结的小MR为2.7％。我们还获得了锰酸铝-钌酸异质结的-16％的反向MR，对应于SrRuO 在 E F 处-9％的负自旋极化> 3 。该观察是费米能级上存在负极化材料的体现，也是朱利叶模型普遍适用性的证明。但是，涉及钌酸的连接处显示出较差的屏障界面均匀性和潜在的界面化合物形成。因此，结点，特别是钌酸同质结，会导致较差的面积和势垒厚度定标，以及严重的磁传输偏倚。这些基于氧化物的结的结果表明，界面均匀性是决定结性能的关键因素。
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