Ji Young Bae

We devised a method to measure the virtual magnetic field induced by Rashba effect in ferromagnetic metal layer. Transverse Rashba magnetic field makes the magnetization direction tilted out of the easy axis, which could be detected by the change in anomalous hall resistances. Through a specified measurement of the second harmonics of the hall resistance, the Rashba field could be obtained with high sensitivity even at low current regime. The results are compared with the prior reports based on the measurement of the transverse field required for the nucleation of reversed domain.

Coping is a strategic approach to dealing with stressful situations. Those who use proactive coping strategies tend to accept changes and act before changes are expected. In contrast, those who use reactive coping are less flexible and more likely to act in response to changes. However, little research has assessed how coping style changes with age. This study investigated age-related changes in coping strategies and stress responsiveness and the influence of age on the processing of conditioned fear memory in 2-, 12- and 23-month-old male mice. Coping strategy was measured by comparing the escape latency in an active avoidance test and by comparing responses to a shock prod. The results showed that proactivity in coping response gradually decreased with age. Stress responsiveness, measured by stress-induced concentration of corticosterone, was also highest in 2-month-old mice and decreased with age. Consolidation of fear memory was highest in 12-month-old mice and was negatively correlated with the degree of stress responsiveness and proactivity in coping. Fear extinction did not differ among age groups and was not correlated with stress responsiveness or the proactivity of coping. However, the maintenance of extinct fear memory, which was best in 2-month-old mice and worst in 12-month-old mice, was negatively correlated with stress responsiveness but not with coping style. Age-dependent changes in the expression of glucocorticoid receptor (GR) and its regulatory co-chaperones, which are accepted mechanisms for stress hormone stimulation, were measured in the hippocampus. The expression of GR was increased at 12 months compared to other age groups. There were no differences in Hsp70 and BAG1 expression by age. These results can be summarized as follows: (1) stress responsiveness and proactivity in coping decreased with age class; (2) consolidation of fear memory was negatively correlated with both stress responsiveness and proactivity; however, maintenance of extinct fear memory was negatively correlated with stress responsiveness only; and (3) consolidation and maintenance of extinct fear memory appeared to be more influenced by factors other than stress reactivity and proactivity in coping, such as the amount of hippocampal glucocorticoid expression.

In the last few years, magnetic tunnel junctions with MgO barrier have attracted attention due to the theoretically predicted and experimentally verified huge TMR. In the present work, crystallization behavior of CoFeB layer adjacent to the MgO or Ru layer was studied by annealing at various temperatures for 1h. The crystallization started at MgO∕CoFeB interface but crystallization temperature changed with materials and thickness of adjacent layer. When the thickness of MgO layer increased in MgO∕CoFeB bilayer, crystallization temperature decreased. This strongly suggests that B from CoFeB layer diffused into adjacent layer to crystallize at lower temperature and MgO can serve as a sink of B. Details will be discussed.

The magnetoresistance (MR) ratio of magnetic tunnel junctions (MTJs) depends on the structure and characteristics of the interface between the ferromagnetic electrode and insulating layer. In order to understand the role of the amorphous CoFeB layer, the MTJs of the following three different pinned layers (PLs) were used: CoFeB (PL1), CoFe/CoFeB/CoFe (PL2) and CoFe (PL3). The MTJs with PL1 and PL2 showed almost the same maximum MR ratio after annealing. This indicates that a smooth or sharp interface has an increased MR ratio. The crystallization temperature of the CoFeB layer showed different dependence on the structure and lattice parameters of the adjacent layer.

We used the job-demand-control model to answer our two research questions concerning the effects of working conditions on self-rated health and gender differences and the association between these working conditions and health among Korean manual workers. Since a disproportionate representation of women in nonstandard work positions is found in many countries, including Korea, it is important to examine how working conditions explain gender inequality in health. We used data from the 2008-2009 Korean National Health and Nutrition Examination Survey and analyzed a total sample of 1,482 men and 1,350 women using logistic regression. We found that job control was positively related to self-rated health, while both physical and mental job demands were negatively related to self-rated health. We also found significant interaction effects of job demands, control, and gender on health. Particularly, female workers' health was more vulnerable to mentally demanding job conditions. We discussed theoretical and practice implications based on these findings.