纳米Fe-In2O3颗粒膜的磁电阻效应和光学特性

研究了射频溅射法制备的纳米Fe-In2O3颗粒膜的磁电阻效应和光学特性。磁电阻测量结果表明：当Fe体积分数为35％时，颗粒膜样品的室温磁电阻变化率△ρρ0达4．5％。通过研究Fe-In2O3颗粒膜样品的透射光谱发现：在In2O3薄膜基体中嵌入纳米铁颗粒的Fe-In2O3颗粒膜中，电子的带问跃迁由In2O3的直接跃迁变为间接跃迁，其带隙随着Fe在颗粒膜中所占体积分数的增加而变窄。     

Giant Magnetoresistance and Its Sensor Applications

Current status is addressed for spin polarized transport such as spin-dependent scattering and spin-dependent tunneling in artificial structured magnetic thin films. The main points discussed include the physical origin of the giant magnetoresistance (GMR) and various GMR materials. The applications of the GMR to magnetic sensors such as read heads for ultra high density magnetic recording are also discussed.     

巨磁电阻材料及其在电子元器件上的应用

介绍了一种新型的磁性功能材料——巨磁电阻薄膜材料,并就它在巨磁电阻传感器、高密度磁记录读磁头以及巨磁电阻随机存储器等电子元器件上的应用作了一些论述。     

Spin‐Structured Multilayers: A New Class of Materials for Precision Spintronics

Magnetoelectronic multilayer devices are widely used in today's information and sensor technology. Their functionality, however, is limited by the inherent properties of magnetic exchange or dipolar coupling which constrain possible spin configurations to collinear or perpendicular alignments of adjacent layers. Here, a deposition procedure is introduced that allows for a new class of layered materials in which complex spin structures can be accurately designed to result in a multitude of new and precisely adjustable spintronic and magnetoresistive properties. The magnetization direction and coercivity of each individual layer are determined by the deposition process in oblique incidence geometry and can be completely decoupled from neighboring layers. This applies for layers of any ferromagnetic material down to layer thicknesses of a few nm and lateral dimensions of a few 100 nm, enabling the design of efficient and compact magnetoelectronic devices, encompassing precision magnetoresistive sensors as well as layer systems with multiple addressable remanent states for magnetic memory applications.     

高迁移率量子阱中声子引起的磁阻震荡

We examine the temperature dependence of acoustic-phonon-induced magnetoresistance oscillations in a high-mobility GaAs-based quantum well with conventional transverse and longitudinal phonon modes, using a model in which the temperature increase of the Landau level broadening or the single-particle scattering rate 1/τ_s is attributed to the enhancement of electron-phonon scattering with rising temperature. The non-monotonic temperature behavior, showing an optimal temperature at which a given order of oscillation amplitude exhibits a maximum and the shift of the main resistance peak to higher magnetic field with rising temperature, is produced, in agreement with recent experimental findings.     

Use of AC Susceptometry to Study Magnetoresistive Properties of Ceramic Samples

In this study we present some results obtained from AC susceptibility (_AC) and transport measurements in polycrystalline samples of La_0.7Ca_0.3MnO₃, in order to better investigate the relations between AC magnetic susceptibility and electrical transport measurements. In addition, it was also studied the inter- and intragranular characteristics of polycrystalline samples. Comparison among results obtained from _AC and transport measurements confirm that is an excellent tool to identify not only sample quality, but also to resolve between intra- and intergranular contributions. Besides that, experiments based on _AC are easier to prepare and perform than those based on the conventional transport measurments. In this context, it is appropriate to establish a link between transport and magnetic properties.     

半掺杂Pr0.5Ca0.5Mn1-xCrxO3体系的电荷有序和磁电阻效应

研究了钙钛矿型半掺杂锰氧化物Pr0.5Ca0.5Mn1-xCrxO3(x=0、0.03、0.05、0.07、0.10)体系的输运性质、电荷有序和磁电阻效应.结果表明,Cr离子替代Mn位,增强了Pr0.5Ca0.5MnO3的铁磁性、金属电导和磁电阻值.在低掺杂情况下(x=0.03、0.05),Cr3 的掺杂使体系的铁磁性增强,当x＞0.05时(x=0.07、0.10),体系的铁磁性随x增大缓慢减弱.同时,随着掺杂量的增大,体系中的电荷有序相逐渐被抑制,磁电阻值也呈下降趋势,表明电荷有序相与磁电阻效应相关.Cr掺杂引起的各种磁耦合作用,包括Mn3 与Cr3 的铁磁双交换作用,Cr3 -Cr3 、Mn4 -Mn4 、Cr3 -Mn4 之间的反铁磁超交换耦合作用及相分离现象是产生上述结果的主要原因.     

Na0．75Co1-xErxO2的磁电阻

NaxCoO2具有奇异热电性质和电磁性质的强关联体系。为进一步探索材料中的电磁性质,制备出Na0．75Co1-xErxO2（0≤x≤0．10）多晶样品。对系统的电阻率、磁电阻和磁化率进行测量,结果显示,加磁场后系统的电阻减小,表明磁性离子对传导电子的散射作用;有效磁矩会随着Er的掺杂浓度增加迅速增大,3％的Er掺杂就能使有效磁矩几乎增大一倍;当系统的磁电阻达到15％,意味着Er的掺杂导致系统出现异常的电磁性质。     

La0.67Sr0.33MnO3中Bi的掺杂效应

将Bi2O3掺杂到用溶胶—凝胶法制备的La0.6Sr0．33MnO3(LSMO)微粉中,XRD测量结果证实有过量的Bi析出。随着Bi掺杂量的增加,LSMO／(Bi2O3)x/2材料电阻率发生明显变化,在x=(0—0．10)摩尔比的掺杂范围内,电阻率先上升后突然下降。当X=0．1时,电阻率比未掺杂样品下降了一个数量级。Bi掺杂对低温和室温磁电阻有着完全不同的影响。低温下,随掺杂量增加,磁电阻下降;室温下Bi的微量掺杂可以使磁电阻增大,掺入x=0.03Bi使室温磁电阻由-4.4％提高到-5．6％。