The exchange bias field of Ta(5)/NiFe(10)/FeMn(20) (nm) multilayer films are investigated as a function of FeMn thickness, where the FeMn layer is etched by Ar ion beam. It was found that the surface roughness is decreased by ion beam etching without the introduction of significant structural damage in the FeMn layer. Exchange bias improvement is observed even at the initiation of FeMn surface etching. The exchange field increases as the etching proceeds and shows maximum at FeMn thickness of 7 nm. The exchange bias begins to decrease with further etching and drops at the FeMn thickness of 5 nm. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The exchange bias of the bottom NiFe layer in NiFe(3 nm)/FeMn(8 nm)/Al(t)/NiFe(t) prepared by rf magnetron sputtering has been investigated as a function of the thickness of the top NiFe and Al layers, where the NiFe and Al thicknesses were varied from 3 to 24 nm and from 0.3 to 2 nm, respectively. The exchange bias of the top NiFe layer is negligible when the Al thickness is larger than 0.3 nm. As the top NiFe thickness increases for a constant Al thickness of 1 nm, the exchange bias of the bottom layer increases from 21.2 to 228.8 Oe for a NiFe thickness of 12 nm, and then decreases with NiFe thickness. An exchange bias of 69.8 Oe for an Al thickness of 0.3 nm increases to 228 Oe on increasing the Al thickness up to 1 nm, and decreases with a further increase of Al thickness. The exchange bias of the bottom NiFe layer could be induced by the interfacial coupling between the bottom NiFe and FeMn layers, but this coupling is strongly dependent on the Al and top NiFe thicknesses, also revealing an anomalous character in the exchange bias of the bottom NiFe layer.

We have investigated the FeMn thickness dependence of the exchange bias in the Py/FeMn/Py structure. The exchange biases of lower and upper Py layers show a difference in strength. The exchange bias of the lower Py is larger than that of the upper Py. The coercivity of the upper Py is larger than that of the lower Py. There are qualitative differences in MFM images according to the strength of exchange bias. The pinning points of MFM images are strongly related with the magnitude of exchange bias and coercivity is a less important parameter.

To establish the efficient cytoplasmic microinjection system in the porcine embryos, pEGFP-N1 plasmid were microinjected into porcine parthenogenetic (PA) and in vitro-fertilized (IVF) embryos to investigate the optimal injection time, volume, and concentration. In experiment 1, to investigate the optimal injection time, development rates were compared among groups of 4 different time durations (2, 4, 6, and 8 hours) in the PA and IVF embryos with time point after activation and sperm removal, respectively. There were no significant differences (P < 0.05) between the 4 groups regarding the cleavage rates. However, there were significant differences (P < 0.05) in development to the blastocysts (4.4, 8.9, 3.9, 0.6%) and GFP expression in blastocysts (1.3, 5.7, 2.3, 0.0%), which was injected after postactivation of 4 hours compared with another 3 groups. The IVF embryos injected after 2 and 4 hours expressed GFP significantly higher than the other two groups, which injected at 6 and 8 hours (P < 0.05). In experiment 2, EGFP-N1 with 2 different concentrations (20 and 50 ng μL–1) was injected in the PA and IVF embryos to investigate the optimal concentration. In PA embryos, there were significant differences in 20 ng μL–1-injected embryos, which had higher cleavage (58.8 v. 41.9%) than blastocysts (13.0 v. 11.1%) and GFP expression rates (P < 0.05). In IVF embryos, GFP were expressed only in 20 ng μL–1 embryos, GFP (4.2%) in the blastocysts showed no significant difference in the cleavage (77.3 v. 64.7%) and blastocyst rates (26.4 v. 23.5%). In experiment 3, three different volumes (5, 10, and 20 pL) were microinjected into porcine embryos to determine the most appropriate volume. Out of 3 groups, significantly higher development rates of cleavage (68.3, 58.0, 29.3%), blastocysts (11.7, 12.7, 0.5%), and GFP-expressed blastocysts (2.9, 7.8, 0.0%) were shown in the 10-pL group (P < 0.05). In conclusion, these results imply that a 20 ng μL–1 concentration, 10 pL of volume, injection 4 hours after activation for PA embryos, as well as injection 2 and 4 hours after sperm removal, a 20 ng μL–1 concentration, and 10 pL of volume for IVF embryos were more effective cytoplasmic microinjection conditions.