Effect of thermal-annealing on the magnetoresistance of manganite-based junctions

Thermal-annealing has been widely used in modulating the oxygen content of manganites. In this work, we have studied the effect of annealing on the transport properties and magnetoresistance of junctions composed of a La0.9Ca0.1MnO3＋6 film and a Nb-doped SrTiO3 substrate. We have demonstrated that the magnetoresistance of junctions is strongly dependent on the annealing conditions： Prom the junction annealed-in-air to the junction annealedin-vacuum, the magnetoresistance near 0-V bias can vary from ～-60% to N～0. A possible mechanism accounting for this phenomenon is discussed.     

Effect of film thickness manganite-based on interfacial barrier of heterojunctions

Interracial barrier is a key factor that determines the performances of heterojunctions. In this work, we study the effect of manganite film thickness on the effective interracial barrier for La0.67Sr0.33MnO3/Nb：SrTiO3 junctions, The barrier is extracted from the forward current-voltage characteristics. Our results demonstrate that the barrier decreases gradually from -0.85 eV to -0.60 eV when the film thickness decreases from 150 nm to 2 nm. The overall value of the barrier is only about 50% of the corresponding one determined from the photovoltaic effect.     

铝的等温状态方程

 采用原位高压同步辐射X射线衍射技术，利用金刚石对顶砧（DAC）装置产生高压，选用高纯NaCl粉末作为传压介质与标压物质，在室温下、21.5 GPa的压力范围内，测定了铝的等温状态方程。利用Murnaghan方程对实验结果进行了数值拟合，得到铝的零压体弹模量及其一级压力导数分别为B₀=(77±2) GPa，B₀′=4.8±0.3。该结果同相关文献资料报导的值在误差范围内符合得很好，略显得较大，这是由于传压介质NaCl的非静水压效应所致。在实验所达到的压力范围内，未发现明显的相变迹象。     

Tuning the electrons at the LaAlO_3/SrTiO_3 interface: From growth to beyond growth

Recently, the quasi-two-dimensional electron gas （q2DEG） confined at the interface between LaAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been used to tune the carrier density and mobility of this q2DEG. These methods can be classified into two categories： growth-related tuning （i.e. substrate, growth temperature, oxygen pressure, post-annealing, LaAlO3 thickness, stoichiometry, and capping layers） and post-growth tuning （i.e. electrostatic field gating, conductive atomic force microscopy and surface adsorbates）. Taken together, these methods enable the broad tuning of the electronic properties of this interface.     

Rotation of ferromagnetic clusters induced magnetoresistance in the junction composed of La0.9Ca0.1MnO3 +δ and 1 wt.% Nb-doped SrTiO3

A junction composed of ultrathin La0.9Ca0.1MnO3＋δ （LCMO） film and 1 wt.% Nb-doped SrTiO3 was fabricated and its magnetoresistance （MR） was studied and compared with LCMO film. It was found that the resistance of the junction has a similar dependence on magnetic field as that of the LCMO film： the curvature of R-H curves is upward above Curie temperature （Tc） and downward below TC. These behaviours strongly suggest that the rotation of ferromagnetic clusters in manganite also causes MR in the corresponding junction. This MR can be qualitatively understood by the change of the width of the barrier induced by the rotation of ferromagnetic clusters. These results suggest a possibility to obtain junctions with large low-field MR.     

Effect of film thickness on interfacial barrier of manganite-based heterojunctions

Interfacial barrier is a key factor that determines the performances of heterojunctions.In this work,we study the effect of manganite film thickness on the effective interfacial barrier for La 0.67 Sr 0.33 MnO 3 /Nb:SrTiO 3 junctions.The barrier is extracted from the forward current-voltage characteristics.Our results demonstrate that the barrier decreases gradually from ～0.85 eV to ～0.60 eV when the film thickness decreases from 150 nm to 2 nm.The overall value of the barrier is only about 50% of the corresponding one determined from the photovoltaic effect.