Se-Chung Oh

Magnetic and Electrical Properties of Magnetic Tunnel Junctions With Radical Oxidized MgO Barriers

This work focuses on magnetic tunnel junctions with a MgO barrier layer made by RF-sputtering and radical oxidation. In case of RF-sputtered MgO, its crystal orientation, MR and RA values very sensitively depend on the chamber atmosphere. The MR ratio of 97% in radical oxidized MgO is obtained at 0.4 V, which is slightly higher than RF-sputtered MgO. Also, its RA is smaller than that of RF-sputtered MgO. These improved MgO properties are originated from the improvement of the crystal orientation of MgO(200) and the decrease of OH component within the MgO barrier. In addition, the breakdown voltage in radical oxidized MgO is higher than that of RF-sputtered MgO at the same MgO thickness

Improved magnetic tunnel junction with amorphous seed layer, surface treatment,and high-polarization magnetic materials

Dependence of magnetic tunnel junction (MTJ) properties on seed layer, surface treatment and magnetic materials was investigated to improve TMR ratio. Roughness of tunnel oxide layer generated from seed layer roughness reduces TMR ratio as well as RA product owing to locally reduced oxide layer thickness. Crystallinity of seed layer is found to be important to enhance TMR ratio. Surface treatment with ion beam etching on a pinned layer improves tunnel oxide uniformity providing higher TMR ratio. Also, highly polarized magnetic material increases TMR ratio but the effect of surface treatment is quite different depending on pinned layer material.

Thermal stability of MTJ using Zr capping layer

The simple stacking structure such as [Sub/Zr/AlO/sub x//NiFe (or CoFeB)/capping layer] was prepared to investigate the changes of magnetic properties of free layer with annealing temperature. Ta, Ru, or Zr was used as the capping layer. Samples were annealed in a vacuum (below 1/spl times/10/sup -6/ Torr) for 1 hour under a magnetic field of 10 KOe. The magnetic properties were measured using vibrating sample magnetometer in sample with 1/spl times/1 cm/sup 2/ area. The changes of the coupling field between the pinned layers through Ru as a function of annealing temperature for various pinned layer materials were also studied.