Low frequency noise in Co/Al2O3〈δ(Fe)〉/Ni80Fe20 magnetic tunnel junctions
نویسندگان
چکیده
Abstract The time dependences, up to 200 s, and the noise power spectrum (0.005–10 Hz) in the electron transport response at bias up to 300 mV of Co/Al2O3/Ni80Fe20 magnetic tunnel junctions (MTJs) and of Co/Al2O3〈δ(Fe)〉/Ni80Fe20 (with Fe δ dopants of thickness 1.8 Å inside the barrier) were investigated. The magnetic field was changed between +100 and −100 G in steps of 1 G. The measurements were carried out at different temperatures between 77 and 300 K for the samples with large tunnel magnetoresistance (exceeding 14% at 300 K). We found that the magnetization reversal of the Co and permalloy electrodes, as detected from the time response near the coercive field, occurs via relaxation on the timescale of about 102 s with sudden jumps in the resistance ( R/R ∼ 10−2–10−3). We link this noise to the depinning of the domain walls. In addition to the magnetic noise, in some of the studied MTJs with Fe δ dopants, we observed a two-level-system telegraph-type noise, which was independent of the magnetic field, indicating its relation to the trapped charges inside the insulating barrier. For MTJs, the noise power spectrum has 1/f α character for a wide frequency range below a few Hz. At low bias and parallel state the exponent α is close to 1–1.5, but at higher bias or in the antiparallel state the exponent increases to 2. We link these effects to non-equilibrium noise in magnetic structure of the electrodes in the antiparallel state and to non-equilibrium transport inside the barrier at high bias.
منابع مشابه
Noise in MgO barrier magnetic tunnel junctions with CoFeB electrodes: Influence of annealing temperature
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 Al2O3 barriers. The origin of the low f...
متن کاملTunnel spin polarization of Ni80Fe20/SiO2 probed with a magnetic tunnel transistor
The tunnel spin polarization of Ni80Fe20/SiO2 interfaces has been investigated using a magnetic tunnel transistor MTT . The MTT with a Ni80Fe20/SiO2 emitter shows a magnetocurrent of 74% at 100 K, corresponding to a tunnel spin polarization of the Ni80Fe20/SiO2 interface of 27%. This is only slightly lower than the value of 34% for Ni80Fe20/Al2O3 interfaces determined in similar MTT structures....
متن کاملLow - frequency noise and inelastic tunneling spectroscopy in Fe ( 1 1 0 ) / MgO ( 1 1 1 ) / Fe ( 1 1 0 ) epitaxial magnetic tunnel junctions
We report on tunnelling magnetoresistance (TMR), current–voltage (IV) characteristics and low-frequency noise in epitaxially grown Fe(1 1 0)/MgO(1 1 1)/Fe(1 1 0) magnetic tunnel junctions (MTJs) with dimensions from 2 2 to 20 20mm. The evaluated MgO energy barrier (0.5070.08 eV), the barrier width (13.170.5 Å) as well as the resistance times area product (771MOmm) show relatively small variatio...
متن کاملStrongly reduced bias dependence in spin–tunnel junctions obtained by ultraviolet light assisted oxidation
For future implementation of ferromagnetic tunnel junctions, we need a better understanding of the influence of the insulating barrier preparation method on the junction resistance, tunnel magnetoresistance ~TMR!, and its voltage bias dependence. In this letter, we focus on the bias dependence of junctions (Co–Al2O3– Ni80Fe20) prepared by ultraviolet light assisted in situ oxidation in an O2 am...
متن کامل