钙钛矿锰氧化物La_1–xSr_xMnO₃ (LSMO)作为一种代表性庞磁阻材料, 在磁传感器等领域具有广阔的应用前景, 但在低磁场和室温下很难获得显著的庞磁阻效应。 为提高LSMO磁电阻效应和转变温度, 本研究采用传统固相反应法制备了La_0.8Sr_0.2Mn_1–xAl_xO₃ (0≤x≤0.25)(LSMAO)多晶样品, 并系统分析了Al³⁺掺杂对LSMO电输运性质和磁电阻效应的影响。X射线衍射(XRD)图谱表明LSMAO样品具有单一的菱方结构, 属于$\text{R}\bar{3}\text{C}$空间群。电输运性质研究发现, 样品的电阻率随Al³⁺的掺杂呈指数型上升, 且外加磁场使金属-绝缘体转变温度有所提高。这可能是由于Al³⁺稀释了Mn³⁺/Mn⁴⁺离子网络, 在减少载流子数量的同时增加了磁无序。此外, LSMAO陶瓷的导电机理随Al³⁺的掺杂从小极化子模型(Small polaron hopping model, SPH)转变成变程跳跃模型(Variable range hopping model, VRH), 说明非磁性的Al³⁺抑制了铁磁团簇间的载流子交换, 使得小极化子热激活近邻跃迁过程被抑制。LSMAO的磁电阻效应从21.03% (x=0)增大到59.71% (x=0.25), 证明Al³⁺掺杂可有效增强LSMAO的磁电阻效应。

Spin injection and detection in bulk GaN were investigated by performing magnetotransport measurements at low temperatures. A non-local four-terminal lateral spin valve device was fabricated with Co/GaN Schottky contacts. The spin injection efficiency of 21% was achieved at 1.7 K. It was confirmed that the thin Schottky barrier formed between the heavily n-doped GaN and Co was conducive to the direct spin tunneling, by reducing the spin scattering relaxation through the interface states.

有机发光二极管（Organic Light-Emitting Diode，OLED）显示器的亮度、色域和显示不均（Mura）等特性与其驱动电流息息相关。为了实现封装后OLED电流的无损检测，本文建立了一种基于隧道磁阻（Tunneling Magnetoresistance，TMR）效应的OLED电流无损检测方法。首先，根据OLED显示器亮度与驱动电流的关系，得到一行像素全部点亮时的驱动电流是40 mA，通过仿真分析40 mA电流的空间磁场分布，估算出TMR磁传感器的灵敏度指标要求。然后，选择TMR2922作为磁传感器，实验研究了点亮双行、多行和单列像素时，显示器磁场与电流的关系、屏幕电磁兼容问题和传感器灵敏度问题。最后，对比分析了不同驱动电流下，TMR2922的磁场数据和Hyperion色度计的光学数据。仿真表明，高度为1.5 mm时磁场传感器的噪声要优于1.1 nT/Hz；实验结果表明，在无屏蔽环境下TMR2922可以检测出OLED mA级的行电流，对于μA级的列电流需要灵敏度更高的磁传感器。

We report the study of magnetic and transport properties of polycrystalline and single crystal Na(Zn,Mn)Sb, a new member of “111” type of diluted magnetic materials. The material crystallizes into Cu₂Sb-type structure which is isostructural to “111” type Fe-based superconductors. With suitable carrier and spin doping, the Na(Zn,Mn)Sb establishes spin-glass ordering with freezing temperature (T_f) below 15 K. Despite lack of long-range ferromagnetic ordering, Na(Zn,Mn)Sb single crystal still shows sizeable anomalous Hall effect belowT_f. Carrier concentration determined by Hall effect measurements is over 10¹⁹ cm^–3. More significantly, we observe colossal negative magnetoresistance (MR ≡ [ρ(H) ? ρ(0)]/ρ(0)) of –94% in the single crystal sample.We report the study of magnetic and transport properties of polycrystalline and single crystal Na(Zn,Mn)Sb, a new member of “111” type of diluted magnetic materials. The material crystallizes into Cu₂Sb-type structure which is isostructural to “111” type Fe-based superconductors. With suitable carrier and spin doping, the Na(Zn,Mn)Sb establishes spin-glass ordering with freezing temperature (T_f) below 15 K. Despite lack of long-range ferromagnetic ordering, Na(Zn,Mn)Sb single crystal still shows sizeable anomalous Hall effect belowT_f. Carrier concentration determined by Hall effect measurements is over 10¹⁹ cm^–3. More significantly, we observe colossal negative magnetoresistance (MR ≡ [ρ(H) ? ρ(0)]/ρ(0)) of –94% in the single crystal sample.

Co-TiO₂纳米复合薄膜作为一种新型自旋电子材料, 由于具有良好的生物相容性, 近年来受到广泛关注。但在制备过程中, 磁性金属Co处于氧化气氛, 容易部分氧化, 从而影响薄膜的隧道磁电阻性能。为了抑制磁性金属的氧化, 提高金属态含量, 本研究通过强磁靶共溅射法制备了Co-TiO₂纳米复合薄膜。该方法采用的强磁靶头, 磁场强度高、分布均匀, 可以提高溅射粒子的能量和溅射速率, 降低因高能粒子碰撞而发生氧化的概率。因此强磁靶共溅射法能明显抑制金属Co的氧化, 提高纳米复合薄膜的自旋极化率。所制备的Co-TiO₂纳米复合薄膜主要由非晶态的TiO₂基体和分散其中的Co颗粒组成。通过调节金属Co颗粒尺寸和分布状态, 在电学上实现了金属态向绝缘态转变, 在磁学上实现了铁磁性向超顺磁性转变。Co含量为51.3at%时, Co-TiO₂纳米复合薄膜表现为高金属态和高电阻率, 并且实现了高达8.25%的室温隧道磁电阻。强磁靶共溅射法使Co-TiO₂纳米复合薄膜的室温磁电阻性能得到了进一步提高, 这对于磁性金属—氧化物纳米复合薄膜的研究有着重要的意义。