Bistable memory effect in chromium oxide junctions
- PDF / 533,930 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 99 Downloads / 190 Views
Q2.10.1
Bistable memory effect in chromium oxide junctions A. Sokolov, C.-S.Yang, E. Ovtchenkov, L. Yuan, S.-H. Liou, B. Doudin University of Nebraska Lincoln, Department of Physics and Astronomy, 115 Brace Laboratory, Lincoln NE 68588-0111
ABSTRACT Magnetotransport properties of granular CrO2 /Cr2O3 films made of CrO2 crystals covered by 1- 2 nm native insulating Cr2O3 are presented. Electrical properties of a limited number of grains measured in series and parallel (10 to 15 grains) reveal intergrain tunneling characteristics. At lowest temperatures, a well pronounced zero bias anomaly indicates that impurities in the junctions block the electronic flow. Hysteresis in the IV curves are observed at intermediate temperatures on zero-field cooled samples. Changing the polarity of a short excitation pulse (100ns) of amplitude smaller than 1 V triggers a change in the zero-bias resistance by 10-50%. These states are stable and well reproducible in the temperature interval ranging from 100K to 250K. Applying an external magnetic field cancels the IV hysteresis. The resistance of the devices in the kΩ range, the potential high-speed for writing and reading the resistance sate, make these systems interesting candidates for magnetic non-volatile memories. INTRODUCTION The integration of magnetic materials in electronic components has become of increasing importance since the boost of research and development efforts initiated by the discovery of giant magnetoresistance effects. This new area of “spintronics” [1] opens the possibility to use magnetic configuration control as an extra degree of freedom for tuning the electric transport properties. The materials with high degree of spin polarization are the most desired for potential application in metal/insulator/metal devices [2], and magnetic multilayer geometries [3, 4]. Chromium dioxide (CrO2) is among the best candidates for half-metallic ferromagnetic systems. Evidence of large spin polarization of conduction electrons has been observed using several methods [5-7]. Magnetoresistance (MR) measurements have been reported in polycrystalline films [8-10], epitaxial films [10- 12] and powder compacts of CrO2[13]. Magnetoresistance values reaching 50% have been observed on CrO2/Cr2O3 composites at low temperature [13]. The results were explained in terms of intergrain tunneling, and the large magnetoresistance (MR) values were attributed to the high degree of spin polarization existing in CrO2. In spite of relatively high Tc, of about 390K, the MR value decays rapidly with increasing temperature and disappointed few percent remains at ambient temperature. A possible explanation of such a behavior is given in terms of Coulomb blockade effects [14]. Another attractive feature of spin-electronic devices is the possibility of current induced magnetization reversal. Injection of spin-polarized electric current can modify the magnetic states of a small ferromagnet. This spin-transfer effect was theoretically predicted by Berger [15] and Slonczewski [16] and there are several exp
Data Loading...
