Magnonic spin-transfer torque MRAM with low power, high speed, and error-free switching

A new class of spin-transfer torque magnetic random access memory (STT-MRAM) is discussed, in which writing is achieved using thermally initiated magnonic current pulses as an alternative to conventional electric current pulses. The magnonic pulses are used to destabilize the magnetic free layer from its initial direction, and are followed immediately by a bipolar electric current exerting conventional spin-transfer torque on the free layer. The combination of thermal and electric currents greatly reduces switching errors, and simultaneously reduces the electric switching current density by more than an order of magnitude as compared to conventional STT-MRAM. The energy efficiency of several possible electro-thermal circuit designs have been analyzed numerically. As compared to STT-MRAM with perpendicular magnetic anisotropy, magnonic STT-MRAM reduces the overall switching energy by almost 80%. Furthermore, the lower electric current density allows the use of thicker tunnel barriers, which should result in higher tunneling magneto-resistance and improved tunnel barrier reliability. The combination of lower power, improved reliability, higher integration density, and larger read margin make magnonic STT-MRAM a promising choice for future non-volatile storage.Comment: 9 Pages, 11 Figure

The effect of the annealing temperature on the local distortion of La0.67_{0.67}Ca0.33_{0.33}MnO3_3 thin films

Mn $K$-edge fluorescence data are presented for thin film samples (3000~\AA) of Colossal Magnetoresistive (CMR) La$_{0.67}$Ca$_{0.33}$MnO$_3$: as-deposited, and post-annealed at 1000 K and 1200 K. The local distortion is analyzed in terms of three contributions: static, phonon, and an extra, temperature-dependent, polaron term. The polaron distortion is very small for the as-deposited sample and increases with the annealing temperature. In contrast, the static distortion in the samples decreases with the annealing temperature. Although the local structure of the as-deposited sample shows very little temperature dependence, the change in resistivity with temperature is the largest of these three thin film samples. The as-deposited sample also has the highest magnetoresistance (MR), which indicates some other mechanism may also contribute to the transport properties of CMR samples. We also discuss the relationship between local distortion and the magnetization of the sample.Comment: 11 pages of Preprint format, 8 figures in one tar fil

Core-Core Dynamics in Spin Vortex Pairs

We investigate magnetic nano-pillars, in which two thin ferromagnetic nanoparticles are separated by a nanometer thin nonmagnetic spacer and can be set into stable spin vortex-pair configurations. The 16 ground states of the vortex-pair system are characterized by parallel or antiparallel chirality and parallel or antiparallel core-core alignment. We detect and differentiate these individual vortex-pair states experimentally and analyze their dynamics analytically and numerically. Of particular interest is the limit of strong core-core coupling, which we find can dominate the spin dynamics in the system. We observe that the 0.2 GHz gyrational resonance modes of the individual vortices are replaced with 2-6 GHz range collective rotational and vibrational core-core resonances in the configurations where the cores form a bound pair. These results demonstrate new opportunities in producing and manipulating spin states on the nanoscale and may prove useful for new types of ultra-dense storage devices where the information is stored as multiple vortex-core configurations

Aiding compliance governance in service-based business processes

Assessing whether a company's business practices conform to laws and regulations and follow standards and SLAs, i.e., compliance management, is a complex and costly task. Few software tools aiding compliance management exist; yet, they typically do not address the needs of who is actually in charge of assessing and understanding compliance. We advocate the use of a compliance governance dashboard and suitable root cause analysis techniques that are specifically tailored to the needs of compliance experts and auditors. The design and implementation of these instruments are challenging for at least three reasons: (1) it is fundamental to identify the right level of abstraction for the information to be shown; (2) it is not trivial to visualize different analysis perspectives; and (3) it is difficult to manage and analyze the large amount of involved concepts, instruments, and data. This chapter shows how to address these issues, which concepts and models underlie the problem, and, eventually, how IT can effectively support compliance analysis in Service-Oriented Architectures (SOAs). © 2012, IGI Global

Determinants in the adult recall of autobiographical childhood memories

This thesis investigated the characteristics of childhood memories that remain accessible over the whole life span. On the assumption that one of the primary purposes of autobiographical memory is its adaptive function, it was hypothesised that, in order to fulfil this function, autobiographical memories must include an affective component. That is, each memory will consist of a record of an experienced event together with the accompanying emotion so as to mediate an appropriate behavioural response in similar future circumstances. For the same reason, it was also predicted that, as a person grows older, selected childhood memories will still retain their emotionality, vividness and personal importance. A detailed analysis of the nature of childhood memories was undertaken and evidence to support these hypotheses was sought in three separate studies. In Study 1, a structured interview was used and 109 people aged between 21 and 91 years were asked to free recall memories drawn from within three - year periods of childhood from birth to 18 years. Subjects' ratings were used to explore the characteristics of these memories and the effects of age encoding subject age and subject gender were systematically examined. In contrast with previous research, it was found that 83 % of subjects could recall memories from below three years of age. Uniformly high ratings of emotionality showed that the affective component, as predicted, was high across all encoding. ages and showed no decline with subject age. Ratings of clarity and realism were also unaffected by subject age. The incidence and vividness of sensory imagery increased with age of encoding, but, again, did not decline with subject age. Although most vivid memories involved imagery, 15%of subjects sometimes claimed to recall vividly without imaging. These findings suggest that the affective component may have been contributing to overall vividness. Study 2 using, cued recall, compared latency of response for emotion cued words and object cued words and also used ratings to examine the characteristics of the retrieved memories. Memories were retrieved Faster to object cues but these memories were still rated high in emotionality. Memories retrieved to emotion cues, although slower to access, were rated as more important, more emotional, more unusual and more frequently recalled. Cue type was therefore shown to be a powerful factor in determining accessibility, overriding other memory characteristics. Although in Studies 1 and 2 subjects selected their own memories, Study 3 tested the retention of details of early experience of school life as designated by the researcher. It was found that detailed memories could still be recalled even in old a`e and that the rate of forgetting declined steadily with age This evidence of persisting retention of early childhood experience is consistent with the view that such memories serve a functional role in that they are an integral part of the 3 individual's self history and developing self concept. The research provides a substantial body of data detailing, the topics recalled From different periods of childhood and the nature of the memories and charts the remarkable stability of these memories across the life span

Spin filtering and magnetoresistance in ballistic tunnel junctions

We theoretically investigate magnetoresistance (MR) effects in connection with spin filtering in quantum-coherent transport through tunnel junctions based on non-magnetic/semimagnetic heterostructures. We find that spin filtering in conjunction with the suppression/enhancement of the spin-dependent Fermi seas in semimagnetic contacts gives rise to (i) spin-split kinks in the MR of single barriers and (ii) a robust beating pattern in the MR of double barriers with a semimagnetic well. We believe these are unique signatures for quantum filtering.Comment: Added references + corrected typo

Spin-polarized tunneling of La0.67Sr0.33MnO3/YBa2Cu3O7-d junctions

The transport properties between ferromagnets and high-Tc superconductors are investigated in La0.67Sr0.33MnO3/YBa2Cu3O7-d (LSMO/YBCO)junctions in the geometry of cross-strip lines. The conductance spectra show zero-bias conductance peaks (ZBCP), reflecting the charge transport in the ab-plane. When an external magnetic field is applied to the junctions, the conductance spectra show two notable features, i.e., an increase of background conductance and an asymmetric ZBCP splitting whose amplitude responds nonlinearly to the applied field. It is shown that the magnetic field response are consistent with a theoretical prediction of tunneling spectroscopy when the presence of a ferromagnetic barrier between a spin-polarized ferromagnet and a d-wave superconductor is assumed.Comment: 10 Pages, 7 EPS figures, Submitted to Phys. Rev.

Argon annealing of the oxygen-isotope exchanged manganite La_{0.8}Ca_{0.2}MnO_{3+y}

We have resolved a controversial issue concerning the oxygen-isotope shift of the ferromagnetic transition temperature T_{C} in the manganite La_{0.8}Ca_{0.2}MnO_{3+y}. We show that the giant oxygen-isotope shift of T_C observed in the normal oxygen-isotope exchanged samples is indeed intrinsic, while a much smaller shift observed in the argon annealed samples is an artifact. The argon annealing causes the 18O sample to partially exchange back to the 16O isotope due to a small 16O contamination in the Ar gas. Such a contamination is commonly caused by the oxygen outgas that is trapped in the tubes, connectors and valves. The present results thus umambiguously demonstrate that the observed large oxygen isotope effect is an intrinsic property of manganites, and places an important constraint on the basic physics of these materials.Comment: 4 pages, 3 figures, submitted to PR