Transport and structural properties of ultrathin films of SrVO 3 (SVO) on SrTiO 3 (001) substrates have been investigated and correlations between Metal-Insulator Transition (MIT) and strain relaxation have been studied.Below a critical thickness, when the film is subjected to tensile strain, the resistivity of the films is increasing with decreasing film thickness. Transport properties evolve from metallic to strongly localized state in several monolayer thick films, showing the bandwidth W control of the Mott-Hubbard transition with the film thickness. Furthermore, a dimensional crossover from 3 Dimensions to 2 Dimensions has been studied by transport measurements. Using Quantum Corrections to the Conductivity (QCC), it is demonstrated that MIT is due to renormalized electron-electron interaction in this material. Finally, for films with the thickness below 6 nm, the confinement provides new effect in magnetotransport with apparition of weak antilocalization in ultrathin films.

Low frequency noise has been measured in magnetic tunnel junctions with MgO barriers and magnetoresistance values up to 235%. The authors investigated the noise for different degrees of crystallization and CoFeB / MgO interface quality depending on the annealing temperature. The authors report an extremely low 1 / f noise, compared to magnetic junctions with Al 2 O 3 barriers. The origin of the low frequency noise is discussed and it is attributed to localized charge traps with the MgO barriers. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2749433͔The resistance of a magnetic tunnel junction ͑MTJ͒ depends on the relative magnetization of the ferromagnetic layers: it is usually low in the parallel configuration ͑PC͒ and high in the antiparallel configuration ͑APC͒. This effect is used for storage in magnetic random access memory and is now being adopted for read heads in place of giant magnetoresistance ͑GMR͒ sensors. The prediction 1,2 and recent observation 3 of tunnel magnetoresistance ͑TMR͒ ratios ͓͑R AP − R P ͒ / R AP ͔ as high as 1000% in MTJs with MgO barrier make those devices very attractive candidates to outclass GMR in high-resolution sensors. However, a high TMR ratio is not enough to make a good magnetoresistive sensor, since its performance is determined by the sensitivity which is the output voltage per unit field divided by the voltage noise.The noise level is as important as the magnitude of the signal itself. From earlier studies on MTJs with Al 2 O 3 barriers, the noise can be traced back to three sources. The first is the frequency-independent thermal noise, which is an intrinsic property of a tunnel junction that defines the ultimate noise limit. Here, we will focus on the two other contributions to the noise, which may be reduced or even eliminated provided the appropriate parameters are known. At low frequencies, noise is dominated by a 1 / f component, which is analogous to 1 / f noise in conductors. It is quantified by the Hooge-like parameter ␣ = AfS V ͑f͒ / V 2 , expressed in units of area; A is the surface area of the junction, S V ͑f͒ the noise power spectrum, and V the voltage drop across the tunnel barrier. Its origin is not fully understood, and, in particular, the influence of magnetization is still unclear although it is commonly observed that ␣ is higher in the APC than in the PC. 4,5 The quality of the metal-barrier interface may also play a role in the 1 / f noise. 4 The third component in MTJs is random telegraphic noise ͑RTN͒, namely, discrete fluctuators in the voltage-time traces associated with a Lorentzian-like spectrum. It is characterized by a strong sample-to-sample random of its amplitude and switching rate and it is interpreted either in terms of charge trapping or magnetic domain fluctuations. 6 In this letter, we discuss low frequency noise properties of MTJs with a MgO barrier which exhibit TMR ratios up to 235%. Our focus is on the annealing temperature, which is the crucial parameter for a high TMR ratio. We discuss the origins of the noise, based on c...