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The autonomous floral promotion pathway plays a key role in the regulation of flowering in rapid-cycling Arabidopsis (Arabidopsis thaliana) by providing constitutive repression of the floral inhibitor FLOWERING LOCUS C (FLC). As a...
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The autonomous floral promotion pathway plays a key role in the regulation of flowering in rapid-cycling Arabidopsis (Arabidopsis thaliana) by providing constitutive repression of the floral inhibitor FLOWERING LOCUS C (FLC). As a result, autonomous pathway mutants contain elevated levels of FLC and are late flowering. Winter annual Arabidopsis, in contrast, contain functional alleles of FRIGIDA (FRI), which acts epistatically to the autonomous pathway to up-regulate FLC and delay flowering. To further explore the relationship between FRI and the autonomous pathway, we placed autonomous pathway mutants in a FRI-containing background. Unexpectedly, we found that a hypomorphic allele of the autonomous pathway gene fy (fy null alleles are embryo lethal) displayed background-specific effects on FLC expression and flowering time; in a rapidcycling background fy mutants contained elevated levels of FLC and were late flowering, whereas in a winter annual background fy decreased FLC levels and partially suppressed the late-flowering phenotype conferred by FRI. Because FY has been shown to have homology to polyadenylation factors, we examined polyadenylation site selection in FLC transcripts. In wild type, two polyadenylation sites were detected and used at similar levels. In fy mutant backgrounds, however, the ratio of products was shifted to favor the distally polyadenylated form. FY has previously been shown to physically interact with another member of the autonomous pathway, FCA. Interestingly, we found that fy can partially suppress FLC expression in an fca null background and promote proximal polyadenylation site selection usage in the absence of FCA. Taken together, these results indicate novel and FCA-independent roles for FY in the regulation of FLC. copy; 2011 American Society.
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A systematic investigation of the switching behavior and writeability characteristics of perpendicular magnetic oxide media was performed by varying the number of oxide layers as well as the anisotropy ${rm K}_{rm u}$ gradient in...
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A systematic investigation of the switching behavior and writeability characteristics of perpendicular magnetic oxide media was performed by varying the number of oxide layers as well as the anisotropy ${rm K}_{rm u}$ gradient in multilayered oxides. The media switching behavior highly depends on the magnetic volume of laterally exchange-coupled cap layer as well as the vertical exchange coupling between oxide and cap layers. The media switching field is significantly reduced with incoherent switching mode. The media writeability is further enhanced by employing the multilayered oxides whose anisotropy values vary. Higher ${rm K}_{rm u}$ graded oxide media exhibits improved resolution, sharper transition, and higher signal-to-noise ratio. An analytical 9-spin model is used to study the impact of anisotropy grading, intergranular and interlayer exchange coupling on writeability and noise performance. The 9-spin model is found to qualitatively agree with the experimental results. Both model and experiment indicate that optimal tuning of the media anisotropy and exchange to the head design is critical in attaining good recording performance.
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We report a systematic study of the switching and recording characteristics of perpendicular magnetic recording media in which the exchange coupling between granular oxide and continuous cap layers was varied. The interfacial exc...
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We report a systematic study of the switching and recording characteristics of perpendicular magnetic recording media in which the exchange coupling between granular oxide and continuous cap layers was varied. The interfacial exchange coupling strength was controlled by adjusting the magnetization $({rm M}_{rm s})$ and the thickness (t) of the exchange control layer (ECL) between granular oxide and cap layers. The media switching mechanism highly depends on the oxide-to-cap exchange coupling strength as well as the relative moment ratio of cap and oxide layers. Reversal process is coherent for medium with only granular oxide layer and becomes incoherent with incorporation of ECL and continuous cap layers. Optimizing granular oxide-to-cap exchange coupling improves the media writeability as well as the media signal-to-noise ratio $({rm SNR}_{rm m})$. At optimum exchange coupling condition, the switching field is significantly reduced even with higher thermal stability factor (${rm K}_{rm u} {rm V/k}_{rm B}$ T). However, when the interlayer coupling strength is too weak, independent switching of oxide and cap layers occurs, resulting in poor writeability and high media noise. An optimum design of oxide-to-cap exchange coupling is critical in attaining recording properties for high density recording through selection of appropriate ECL and cap materials.
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We have experimentally and analytically studied the writeability and recording characteristics of perpendicular magnetic recording media in which the anisotropy $({rm K}_{rm u})$ of the granular oxides and the magnetization $({rm ...
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We have experimentally and analytically studied the writeability and recording characteristics of perpendicular magnetic recording media in which the anisotropy $({rm K}_{rm u})$ of the granular oxides and the magnetization $({rm M}_{rm s})$ and lateral exchange coupling $({rm A}_{rm ex})$ of the cap layer were varied. The analytical results are obtained with a 9-spin model, which consists of 3 grains with 3 layers each, representing dual oxide media with a capping layer. The 9-spin model estimates bit error rate (BER) using an error-pattern-correcting code (EPCC) based iterative channel model. The experimental results qualitatively agree well with the analytical results of the 9-spin model. High ${rm K}_{rm u}$ gradient oxides and high ${rm M}_{rm s}$ cap layer improve writeability and BER, whereas high ${rm A}_{rm ex}$ in the cap layer degrades switching field distribution and off-track capability. Media switching field and switching field distribution strongly depend on spatial distribution of the external field. Both experimental and analytical results indicate that an appropriate design of ${rm K}_{rm u}$ graded media with an optimum cap layer can effectively reduce jitter and switching field distribution for given head fields, resulting in higher recording density.
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A new underlayer structure consisting of a magnetic seed was used to reduce the recording layer-to-soft magnetic underlayer (RTS) spacing and its effect on perpendicular recording characteristics was investigated. The RTS spacing ...
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A new underlayer structure consisting of a magnetic seed was used to reduce the recording layer-to-soft magnetic underlayer (RTS) spacing and its effect on perpendicular recording characteristics was investigated. The RTS spacing is reduced by partially replacing the non-magnetic FCC NiW alloy layer with a magnetic CoNiFe layer that acts as a part of the underlying SUL through magnetic exchange coupling. Magnetic CoNiFe layer promotes predominant FCC (111) planes of NiW layer that enhances epitaxial growth of the subsequent Cr BCC (110), Ru and Co HCP (0002) layers. As a result of improved crystallography with magnetic seed, the Co (0002) c axis dispersion is reduced at lower RTS spacing. The head write-ability becomes stronger at lower RTS spacing and the influence of side fringing fields on the nearest adjacent track erasure is highly dependent on the write head type at different RTS spacing. In addition, the change in RTS spacing also affects the read-back response. The signal-to-media noise (SNRm) is improved at low linear densities regardless of RTS spacing but degrades at higher linear densities when RTS spacing becomes too low. It is important to optimize the RTS spacing and the head-to-media integration to improve overall system performance.
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In this study, a new underlayer structure consisting of FCC NiW, BCC Cr and HCP Ru layers is investigated as a promising underlayer that offers good perpendicular magnetic and recording properties. The FCC (111) planes of NiW laye...
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In this study, a new underlayer structure consisting of FCC NiW, BCC Cr and HCP Ru layers is investigated as a promising underlayer that offers good perpendicular magnetic and recording properties. The FCC (111) planes of NiW layer enhances hetero-epitaxial growth of the subsequent BCC Cr (110), HCP Ru and Co (0002) layers in the direction perpendicular to the film plane. After the NiW–Cr–Ru layer structure is optimized, the Co (0002) $c$ axis dispersion is greatly reduced and $sim$ 3 degree of XRD rocking width is achieved. As a result, excellent magnetic properties such as high coercivity, high nucleation field and narrow switching field distribution (SFD) are obtained. In addition, low media jitter and high signal-to-media noise $({rm SNR}_{ m})$ can be achieved. The ${rm SNR}_{ m}$ is also highly dependent on head-to-SUL spacing which is altered by varying NiW or Cr layer thickness without affecting crystallography. Optimized head-to-SUL spacing is needed to gain head writeability as well as resolution.
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Exchange coupled composite (ECC) media have been proposed as a way to facilitate writing of perpendicular media to allow use of magnetic materials with higher magnetic anisotropy $({K}_{u})$ to increase media thermal stability. T...
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Exchange coupled composite (ECC) media have been proposed as a way to facilitate writing of perpendicular media to allow use of magnetic materials with higher magnetic anisotropy $({K}_{u})$ to increase media thermal stability. This paper is an experimental study of ECC media. Our results show that overwrite (OW) of perpendicular media can be improved significantly by the addition of an exchange control layer (ECL), consistent with the original ECC media design proposal. However, such OW improvement can also be achieved with non-ECC media (without ECL) by thickening of the cap magnetic layer. We observe that at similar OW, the non-ECC media can have similar magnetic core width (MCW) to ECC media with even higher thermal decay energy barrier (${K}_{u}$V/kT). The advantage of the ECC media is, instead, media signal-to-noise ratio increase over the non-ECC media. It is also observed that magnetic property and recording performance of the ECC media strongly depend on the magnetic properties and thicknesses of both ECL and cap magnetic layer.
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A systematic investigation of the magnetic and recording characteristics of reactively sputtered CoPtCr-(Si-O, Ti-O, Cr-O) media has been performed. The optimum oxidation condition for media with well-isolated Co grains, high coer...
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A systematic investigation of the magnetic and recording characteristics of reactively sputtered CoPtCr-(Si-O, Ti-O, Cr-O) media has been performed. The optimum oxidation condition for media with well-isolated Co grains, high coercivity$( H_ c)$and nucleation field$( H_ n)$, and superior media noise performance strongly depends on the oxide type. Despite differences in the optimum oxidation condition, the highest achievable$ H_ c$and$ H_ n$are similar. The transition jitter and magnetic write width are mainly determined by the magnetic exchange coupling depending on the oxidation condition but not by the oxide type.
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Magnetic patterns on perpendicular recording media were imaged by spin-stand level dynamic read-back microscopy. High-density tracks are clearly resolved up to 1000 kfci and details of magnetic bit structure, not usually observabl...
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Magnetic patterns on perpendicular recording media were imaged by spin-stand level dynamic read-back microscopy. High-density tracks are clearly resolved up to 1000 kfci and details of magnetic bit structure, not usually observable using standard read-write tests, are readily observed. Encroachment of tracks on Co-Cr-Pt-O media with low oxygen content and low-coercivity results in a nonuniform erasure; as-written rectangular bits become trapezoidal in shape. Media with high oxygen content and high coercivity provide superior side erasure resistance.
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The effect of magnetostriction (MS) on the device characteristics of soft-adjacent-layer (SAL) biased magnetoresistive (MR) head was investigated. As MS changes from -7/spl times/10/sup -7/ to 1.77/spl times/10/sup -6/, the magnet...
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The effect of magnetostriction (MS) on the device characteristics of soft-adjacent-layer (SAL) biased magnetoresistive (MR) head was investigated. As MS changes from -7/spl times/10/sup -7/ to 1.77/spl times/10/sup -6/, the magnetic track width increases from 1.26 to 1.83 /spl mu/m. Asymmetry of bias point, output sensitivity, and output amplitude are also affected by the stress induced anisotropy. The variation of magnetostriction (/spl Delta//spl lambda/=2/spl times/10/sup -6/) induces the change in bias field by 60 Oe associated with the estimated stress of +800 MPa on the MR stripe.
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