2,039 research outputs found
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Magnetic Properties and Interfacial Anisotropies of Pt/Co/AlO<inf>x</inf> Perpendicularly Magnetized Thin Films
The thin films of Pt/Co/AlOx, showing perpendicular magnetic anisotropy, were grown by magnetron sputtering with AlOx formed by the oxidation of thin Al layers using an oxygen atom source. Films were studied as a function of Pt thickness and Al oxidation, and films that showed full remanence and sharp switching coercivity were achieved. In order to prevent further oxidation of the interface in ambient conditions, we use a double Al growth and oxidation process. The magnetooptical Kerr effect and vibrating sample magnetometry were used to analyze these films. We find an effective perpendicular anisotropy of 2 × 106 erg/cm3, with the majority of the perpendicular anisotropy coming from the Pt/Co interface. From the sweep rate dependence on the coercivity, we are able to extract an activation volume of 4.3-0.5 × 10-18cm3, similar to other Co-based perpendicular systems.This research is funded by the European Community under the Seventh Framework Program ERC Contract No. 247368: 3SPIN. AB acknowledges DTA funding from the EPSRC
Entretien avec Robin Mansell
Version anglaise disponible dans la Bibliothèque numérique du CRDI: In conversation with Dr. Robin Mansel
Experiences of a transdiagnostic group, the Take Control Course, for clients with common mental health problems : a qualitative study
Objectives
Despite the promising effectiveness findings for transdiagnostic groups, studies have not explored clients' experiences. There is a risk that clients could perceive that the content of transdiagnostic groups is not sufficiently tailored to their specific problems. Our aims were to examine whether a brief transdiagnostic group, the Take Control Course (TCC), was acceptable to participants and to explore participants' perceptions of psychological change.
Methods
Qualitative data were collected via 12 semistructured, in‐depth interviews. Data collection and thematic analysis were concurrent and iterative.
Results
Three superordinate themes were identified: “Style and format,” “Control and flexibility,” and “Change.” The flexible group format was appreciated, as participants felt able to engage at their own pace and adapt relevant aspects. Greater clarity regarding what was within participants' control reduced distress and enabled effective pursuit of valued goals. Participants described significant (predominantly gradual) changes, including substantial improvements within relationships.
Conclusions
The transdiagnostic format did not prevent participants experiencing the TCC as individually relevant. The flexibility and consistent theoretical framework seemed to contribute to this. The results indicated that greater consideration of control and mindfulness allowed greater cognitive flexibility, an ability to reprioritize and let go of unhelpful habits, which better enabled participants to meet their goals. Implications for group therapy include (a) clearly explaining the format of such groups to clients and (b) providing flexibility in the way the group is delivered where possible. Additional qualitative studies of transdiagnostic groups are required to establish if themes generalize to other transdiagnostic groups
In conversation with Dr. Robin Mansell
French version available in IDRC Digital Library: Entretien avec Robin Mansel
Disentangling surface and bulk transport in topological-insulator - junctions
By combining -type and -type
topological insulators, vertically stacked - junctions can be formed,
allowing to position the Fermi level into the bulk band gap and also tune
between - and -type surface carriers. Here we use low-temperature
magnetotransport measurements to probe the surface and bulk transport modes in
a range of vertical heterostructures with varying
relative thicknesses of the top and bottom layers. With increasing thickness of
the layer we observe a change from - to -type
behavior via a specific thickness where the Hall signal is immeasurable.
Assuming that the the bulk and surface states contribute in parallel, we can
calculate and reproduce the dependence of the Hall and longitudinal components
of resistivity on the film thickness. This highlights the role played by the
bulk conduction channels which, importantly, cannot be probed using surface
sensitive spectroscopic techniques. Our calculations are then buttressed by a
semi-classical Boltzmann transport theory which rigorously shows the vanishing
of the Hall signal. Our results provide crucial experimental and theoretical
insights into the relative roles of the surface and bulk in the vertical
topological - junctions.Comment: 11 pages, 5 figure
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Two-dimensional control of field-driven magnetic bubble movement using Dzyaloshinskii-Moriya interactions
The field-induced asymmetric growth of magnetic bubble domains in Pt/Co/Pt out-of-plane magnetized films with Dzyaloshinskii–Moriya interactions (DMI) is used to control the lateral displacement of bubbles. We demonstrate experimentally that we can laterally translate bubbles away from their nucleation site by applying a series of alternating 3-dimensional field pulses with a controlled relative sign between the out-of-plane and in-plane components. Using magneto optical Kerr effect imaging, the domain wall velocity as a function of applied field strength was measured from which the magnitude of the DMI field was estimated.This work was supported by the European Community
under the Seventh Framework Programme '3SPIN' (ERC
contract 247368) and by EMRP JRP EXL04 SpinCal.
The EMRP is jointly funded by the EMRP participating
countries within EURAMET and the EU.This is the accepted manuscript. The final version is available from AIP at http://scitation.aip.org/content/aip/journal/apl/106/2/10.1063/1.4905600
Sputter grown Fe and Fe/Cr multilayers with fourfold magnetic anisotropy on GaAs
Thin films of Fe have been epitaxially sputtered on GaAs substrates with native oxide removal prior to the deposition carried out by an Ar ion milling. Films grown at substrate temperatures above 100 °C show well-defined fourfold anisotropies. The onset of epitaxial growth is accompanied by an increase in the surface roughness with growth occurring in a distinct island-like pattern. The Fe layers show significantly reduced moments, which decrease with increasing temperature. Antiferromagnetic coupling between Fe layers with Cr spacers was measured in a multilayer with a Cr thickness of 2.7 nm, around the second antiferromagnetic peak. The magnetic properties of the films are discussed in the context of multilayer storage applications
Controlling the canted state in antiferromagnetically coupled magnetic bilayers close to the spin reorientation transition
Canted magnetization is obtained in ultrathin, antiferromagnetically coupled magnetic bilayers with thicknesses around the spin reorientation transition. The canting angle is controlled by both the magnetic layer thickness and interlayer coupling strength, which are tuned independently. Hysteresis loops are obtained, where magnetization components parallel and transverse to the applied field are measured, and analyzed by comparison to micromagnetic simulations. This enables the canting angle to be extracted and the behavior of the individual layers to be distinguished. Two types of canted systems are obtained with either single-layer reversal or complex, coupled two-layer reversal, under moderate external magnetic fields. Controlling the magnetization canting and reversal behavior of ultra-thin layers is relevant for the development of magnetoresistive random-access memory and spin-torque oscillator devices
Depolarization of sperm membrane potential is a common feature of men with subfertility and is associated with low fertilization rate at IVF
STUDY QUESTION. Are significant abnormalities in outward (K+) conductance and resting membrane potential (Vm) present in the spermatozoa of patients undertaking IVF and ICSI and if so, what is their functional effect on fertilization success? SUMMARY ANSWER. Negligible outward conductance (≈5% of patients) or an enhanced inward conductance (≈4% of patients), both of which caused depolarization of Vm, were associated with a low rate of fertilization following IVF. WHAT IS KNOWN ALREADY. Sperm-specific potassium channel knockout mice are infertile with defects in sperm function, suggesting that these channels are essential for fertility. These observations suggest that malfunction of K+ channels in human spermatozoa might contribute significantly to the occurrence of subfertility in men. However, remarkably little is known of the nature of K+ channels in human spermatozoa or the incidence and functional consequences of K+ channel defects. STUDY DESIGN, SIZE AND DURATION. Spermatozoa were obtained from healthy volunteer research donors and subfertile IVF and ICSI patients attending a hospital assisted reproductive techniques clinic between May 2013 and December 2015. In total, 40 IVF patients, 41 ICSI patients and 26 normozoospermic donors took part in the study. PARTICIPANTS/MATERIALS, SETTING, METHODS. Samples were examined using electrophysiology (whole-cell patch clamping). Where abnormal electrophysiological characteristics were identified, spermatozoa were further examined for Ca2+ influx induced by progesterone and penetration into viscous media if sufficient sample was available. Full exome sequencing was performed to specifically evaluate potassium calcium-activated channel subfamily M α 1 (KCNMA1), potassium calcium-activated channel subfamily U member 1 (KCNU1) and leucine-rich repeat containing 52 (LRRC52) genes and others associated with K+ signalling. In IVF patients, comparison with fertilization rates was done to assess the functional significance of the electrophysiological abnormalities. MAIN RESULTS AND THE ROLE OF CHANCE. Patch clamp electrophysiology was used to assess outward (K+) conductance and resting membrane potential (Vm) and signalling/motility assays were used to assess functional characteristics of sperm from IVF and ICSI patient samples. The mean Vm and outward membrane conductance in sperm from IVF and ICSI patients were not significantly different from those of control (donor) sperm prepared under the same conditions, but variation between individuals was significantly greater (P< 0.02) with a large number of outliers (>25%). In particular, in ≈10% of patients (7/81), we observed either a negligible outward conductance (4 patients) or an enhanced inward current (3 patients), both of which caused depolarization of Vm. Analysis of clinical data from the IVF patients showed significant association of depolarized Vm (≥0 mV) with low fertilization rate (P= 0.012). Spermatozoa with electrophysiological abnormities (conductance and Vm) responded normally to progesterone with elevation of [Ca2+]i and penetration of viscous medium, indicating retention of cation channel of sperm (CatSper) channel function. LIMITATIONS, REASONS FOR CAUTION. For practical, technical, ethical and logistical reasons, we could not obtain sufficient additional semen samples from men with conductance abnormalities to establish the cause of the conductance defects. Full exome sequencing was only available in two men with conductance defects. WIDER IMPLICATIONS OF THE FINDINGS. These data add significantly to the understanding of the role of ion channels in human sperm function and its impact on male fertility. Impaired potassium channel conductance (Gm) and/or Vm regulation is both common and complex in human spermatozoa and importantly is associated with impaired fertilization capacity when the Vm of cells is completely depolarized
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