Influence of R.F. sputter parameters on the magnetic orientation of Co-Cr layers

Co-Cr layers for the perpendicular recording mode were deposited by means of RF-sputtering. The most important sputter parameters, i.e. the RF sputter high voltage VRF, the argon pressure Parand the substrate holder temperature Tsh, gave an optimum value for perpendicular orientation of the magnetization. The crystal structure is always hcp within the ranges of varied parameters and no other magnetic phases were observed. If the sputter parameters do not have optimum values an additional hcp compound with in-plane orientation of the c-axis is observed. This orientation causes an increase of the in-plane remanenceS//= (M_{r}/M_{s}). Measurements of the substrate temperature Tsas an function of the various sputter parameters lead to the conclusion that an exclusive perpendicular c-axis orientation is only obtained atT_{s} sim 15thetadegc. At other Tsestablished either directly by changing Tshor indirectly by changing the sputter conditions an additional hcp compound with in-plane c-axis orientation appears. We concluded that Tsis the dominant parameter for sputtering CoCr layers

Characteristics of RF-sputtered CoCr films

The magnetization of the CoCr recording medium has been investigated by several methods. First the perpendicular hysteresis loops are analysed in the thickness range from 500 to 20,000 Å. This provided evidence that the magnetization process is typefied by domain wall motion. Second the dependence of the coercivity on the film thickness has been determined. The dependence found can be explained if it is assumed, that the coercivity is caused by domain walls, impeded by the crystallite boundaries. Finally stand-still recording experiments have been performed, which confirm that magnetization takes place by the displacement of domain walls. The switching criterion in the writing process is best met by taking the field averaged over the film thickness

Co-Cr films for perpendicular recording

Co-Cr films were prepared by means of RF-sputtering. The dependence of the magnetic parameters on the sputter conditions was investigated. It was found that for increasing Ar-pressure the c-axis of the hcp-structure gradually declines from normal to in-plane orientation. An optimum for the sputter voltage is found. The coercivity increases with decreasing target-substrate distance and this is probably due to surface heating by electron bombardment from the Ar-plasma. The recording characteristics of these Co-Cr films were then investigated by means of stand-still recording experiments. A 6.7 mm thick permalloy single-pole head (SPH) was used for creating a head print in a 1 mm thick Co-Cr layer. The flux reversals are detected by means of a magneto-resistive transducer (MRT). The response was analyzed, using a analytical method for calculating the magnetization distribution in the Co-Cr layer. For this purpose the head field of the SPH was also determined with the same MRT

Multiphoton Coincidence Spectroscopy

We extend the analysis of photon coincidence spectroscopy beyond bichromatic excitation and two-photon coincidence detection to include multichromatic excitation and multiphoton coincidence detection. Trichromatic excitation and three-photon coincidence spectroscopy are studied in detail, and we identify an observable signature of a triple resonance in an atom-cavity system.Comment: 6 page, REVTeXs, 6 Postscript figures. The abstract appeared in the Proceedings of ACOLS9

Giardia assemblage A: human genotype in muskoxen in the Canadian Arctic

As part of an ongoing program assessing the biodiversity and impacts of parasites in Arctic ungulates we examined 72 fecal samples from muskoxen on Banks Island, Northwest Territories, Canada for Giardia and Cryptosporidium. Cryptosporidium spp. were not detected, but 21% of the samples were positive for Giardia. Sequencing of four isolates of Giardia demonstrated G. duodenalis, Assemblage A, a zoonotic genotype

Genotyping of Giardia in Dutch patients and animals: a phylogenetic analysis of human and animal isolates.

Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis) is a protozoan organism that can infect the intestinal tract of many animal species including mammals. Genetic heterogeneity of G. duodenalis is well described but the zoonotic potential is still not clear. In this study, we analysed 100 Giardia DNA samples directly isolated from human stool specimens, to get more insight in the different G. duodenalis assemblages present in the Dutch human population. Results showed that these human isolates could be divided into two main Assemblages A and B within the G. duodenalis group on the basis of PCR assays specific for the Assemblages A and B and the DNA sequences of 18S ribosomal RNA and the glutamate dehydrogenase (gdh) genes. Genotyping results showed that G. duodenalis isolates originating from Dutch human patients belonged in 35% of the cases to Assemblage A (34/98) and in 65% of the cases to Assemblage B (64/98) whereas two human cases remained negative in all assays tested. In addition, we compared these human samples with animal samples from the Netherlands and human and animal samples from other countries. A phylogenetic analysis was carried out on the DNA sequences obtained from these Giardia and those available in GenBank. Using gdh DNA sequence analysis, human and animal Assemblage A and B Giardia isolates could be identified. However, phylogenetic analysis revealed different sub-clustering for human and animal isolates where host-species-specific assemblages (C, D, E, F and G) could be identified. The geographic origin of the human and animal samples was not a discriminating factor