K.I. Lee

Enhanced tunneling magnetoresistance and thermal stability of magnetic tunnel junction by rapid thermal anneal

Abstract The effect of rapid thermal anneal (RTA) has been investigated on the properties of an FeMn exchange-biased magnetic tunnel junction (MTJ) using magnetoresistance and I – V measurements and transmission electron microscopy (TEM). The tunneling magnetoresistance (TMR) in an as-grown MTJ is found to be ∼27%, while the TMR in MTJs annealed by RTA increases with annealing temperature up to 300°C, reaching ∼46%. TEM images reveal that the interface of Al 2 O 3 layer for the annealed MTJ has changed into a relatively clear morphology, as compared to that for the as-grown MTJ. The oxide barrier parameters are found to vary abruptly with annealing time within a few ten seconds. Our results demonstrate that the present RTA enhances the thermal stability of MTJs.

Temperature dependence of magnetoresistance for tunnel junctions with high-power plasma-oxidized barriers: Effects of annealing

Magnetic tunnel junctions (MTJ) were fabricated with high oxygen-plasma power and the effects of annealing on the temperature dependence of tunneling magnetoresistance (TMR) were investigated experimentally. As grown, TMR increases, peaks around 160 K, and decreases with increasing temperature from 80 K to 300 K. When MTJs are annealed, Tmax, the temperature at which maximum TMR is obtained, decreases as annealing temperature increases to the optimal point. In order to explain the temperature dependence of TMR, the difference of conductance between parallel and antiparallel alignments of magnetizations as a function of temperature is also analyzed. The shifts of Tmax due to annealing are described phenomenologically with spin-dependent transfer rates of electrons through the barrier.

Ferromagnetic ordering of n-type (Ga,Mn)N epitaxial films

The magnetic and magnetotransport properties of epitaxial (Ga1-xMnx)N films with low Mn concentration (x=0.06- 0.5%) grown by plasma-enhanced molecular beam epitaxy have been investigated. Ferromagnetic ordering for the GaMnN is clearly seen in the temperature range 4-300 K. The M-T curves were fitted with theoretical equations based on the mean field theory in order to estimate Curie temperature (Tc), providing Tc≈550 K and Tc≈700 K, respectively, for the (Ga,Mn)N films with x=0.16% and x=0.50%. Temperature dependence of sheet resistance is found to show negative magnetoresistance in the temperature range 4-300 K, indicative of ferromagnetic semiconducting (Ga,Mn)N films.

Optimization of tunneling magnetotransport and thermal properties in magnetic tunnel junctions by rapid thermal anneal

We report on a systematic investigation of rapid thermal anneal (RTA) effects on the properties of FeMn exchange-biased magnetic tunnel junctions (MTJs). The tunneling magnetoresistance (TMR) in an as-grown MTJ is found to be ∼27%, whereas the TMR in MTJs annealed by RTA increases with annealing temperature up to 300°C, reaching ∼46%. A significant change in the effective barrier thickness (teff) and height (Φeff) occurs within 10 s during RTA. Transmission electron microscopy and X-ray reflectivity studies demonstrate that the interface of the alumina tunnel barrier for the MTJ annealed by RTA became sharper and clearer, giving rise to the enhanced TMR.

Experimental and simulation study of Cu-Al NOL for CCP-CPP-GMR spin-valve

In this study, we introduce the energy application such as annealing on the Al as deposition state and from molecular dynamics (MD) simulations, the details of atomic configurations for Al atoms on Cu(l 11) surface were investigated. Using this method we can control the size of the Al grains, and, hence, the CCP phenomena can be controlled and improved.The current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect has been greatly attracted for its application to ultra high density storage devices.

Magnetotransport in an n-type diluted magnetic semiconductor: (Ga,Mn)N

In this paper, magnetotransport in the ferromagnetic epitaxial (Ga,Mn)N films grown by plasma-enhanced molecular beam epitaxy (PEMBE) was reported. The variation of magnetoresistance (/spl Delta/R/R) with magnetic fields applied perpendicular to the sample was reported.

Magnetotransport of semimetallic Bi thin films grown by electroplating and sputtering

In this paper, we present the magnetotransport properties of the electroplated and sputtered Bi thin film in the temperature range 4-300 K.

Abnormal Temperature Dependence of Tunneling Magnetoresistance for Magnetic Tunnel Junctions

Magnetic tunnel junctions (MTJs) were fabricated with high bias for plasma oxidation and the effects of annealing on the temperature dependence of tunneling magnetoresistance (TMR) were investigated experimentally. As-grown, TMR increases, peaks around 160 K, and decreases with increasing temperature from 80 K to 300 K. When MTJs are annealed, Tmax, the temperature at which maximum TMR is obtained, decreases as annealing temperature increases to the optimal point. In order to explain this abnormal temperature dependence of TMR, the difference of conductance between parallel and antiparallel alignments of magnetizations as a function of temperature is also analyzed. The shifts of Tmax due to annealing process are described phenomenologically with spin-dependent transfer rates of electrons tunnel through the barrier.