Temperature dependent nucleation and propagation of domain walls in a sub-100 nm perpendicularly magnetized Co/Ni multilayer

We present a study of the temperature dependence of the switching fields in Co/Ni-based perpendicularly magnetized spin-valves. While magnetization reversal of all-perpendicular Co/Ni spin valves at ambient temperatures is typically marked by a single sharp step change in resistance, low temperature measurements can reveal a series of resistance steps, consistent with non-uniform magnetization configurations. We propose a model that consists of domain nucleation, propagation and annihilation to explain the temperature dependence of the switching fields. Interestingly, low temperature (<30 K) step changes in resistance that we associate with domain nucleation, have a bimodal switching field and resistance step distribution, attributable to two competing nucleation pathways.Comment: 5 pages, 4 figure

Characterization of the Intra-Unit-Cell magnetic order in Bi2Sr2CaCu2O8+d

As in YBa2Cu3O6+x and HgBa2CuO8+d, the pseudo-gap state in Bi2Sr2CaCu2O8+d is characterized by the existence of an intra-unit-cell magnetic order revealed by polarized neutron scattering technique. We report here a supplementary set of polarized neutron scattering measurements for which the direction of the magnetic moment is determined and the magnetic intensity is calibrated in absolute units. The new data allow a close comparison between bilayer systems YBa2Cu3O6+x and Bi2Sr2CaCu2O8+d and rise important questions concerning the range of the magnetic correlations and the role of disorder around optimal doping.Comment: 12 pages, 8 figures, submitted to physical review

Distortion of the Stoner-Wohlfarth astroid by a spin-polarized current

The Stoner-Wohlfarth astroid is a fundamental object in magnetism. It separates regions of the magnetic field space with two stable magnetization equilibria from those with only one stable equilibrium and it characterizes the magnetization reversal of nano-magnets induced by applied magnetic fields. On the other hand, it was recently demonstrated that transfer of spin angular momentum from a spin-polarized current provides an alternative way of switching the magnetization. Here, we examine the astroid of a nano-magnet with uniaxial magnetic anisotropy under the combined influence of applied fields and spin-transfer torques. We find that spin-transfer is most efficient at modifying the astroid when the external field is applied along the easy-axis of magnetization. On departing from this situation, a threshold current appears below which spin-transfer becomes ineffective yielding a current-induced dip in the astroid along the easy-axis direction. An extension of the Stoner-Wohlfarth model is outlined which accounts for this phenomenon.Comment: 8 pages, 6 figure

Two types of all-optical magnetization switching mechanisms using femtosecond laser pulses

Magnetization manipulation in the absence of an external magnetic field is a topic of great interest, since many novel physical phenomena need to be understood and promising new applications can be imagined. Cutting-edge experiments have shown the capability to switch the magnetization of magnetic thin films using ultrashort polarized laser pulses. In 2007, it was first observed that the magnetization switching for GdFeCo alloy thin films was helicity-dependent and later helicity-independent switching was also demonstrated on the same material. Recently, all-optical switching has also been discovered for a much larger variety of magnetic materials (ferrimagnetic, ferromagnetic films and granular nanostructures), where the theoretical models explaining the switching in GdFeCo films do not appear to apply, thus questioning the uniqueness of the microscopic origin of all-optical switching. Here, we show that two different all-optical switching mechanisms can be distinguished; a "single pulse" switching and a "cumulative" switching process whose rich microscopic origin is discussed. We demonstrate that the latter is a two-step mechanism; a heat-driven demagnetization followed by a helicity-dependent remagnetization. This is achieved by an all-electrical and time-dependent investigation of the all-optical switching in ferrimagnetic and ferromagnetic Hall crosses via the anomalous Hall effect, enabling to probe the all-optical switching on different timescales.Comment: 1 page, LaTeX; classified reference number

DEFEAT-polypharmacy:deprescribing anticholinergic and sedative medicines feasibility trial in residential aged care facilities

Background Prolonged use of anticholinergic and sedative medicines is correlated with worsening cognition and physical function decline. Deprescribing is a proposed intervention that can help to minimise polypharmacy whilst potentially improving several health outcomes in older people. Objective This study aimed to examine the feasibility of implementing a deprescribing intervention that utilises a patient-centred pharmacist-led intervention model; in order to address major deprescribing challenges such as general practitioner time constraints and lack of accessible deprescribing guidelines and processes. Setting Three residential care facilities. Methods The intervention involved a New Zealand registered pharmacist utilising peer-reviewed deprescribing guidelines to recommend targeted deprescribing of anticholinergic and sedative medicines to GPs. Main outcome measure The change in the participants' Drug Burden Index (DBI) total and DBI 'as required' (PRN) was assessed 3 and 6 months after implementing the deprescribing intervention. Results Seventy percent of potential participants were recruited for the study (n = 46), and 72% of deprescribing recommendations suggested by the pharmacist were implemented by General Pratitioners (p = 0.01; Fisher's exact test). Ninety-six percent of the residents agreed to the deprescribing recommendations, emphasising the importance of patient centred approach. Deprescribing resulted in a significant reduction in participants' DBI scores by 0.34, number of falls and adverse drug reactions, 6 months post deprescribing. Moreover, participants reported lower depression scores and scored lower frailty scores 6 months after deprescribing. However, cognition did not improve; nor did participants' reported quality of life. Conclusion This patient-centred deprescribing approach, demonstrated a high uptake of deprescribing recommendations and success rate. After 6 months, significant benefits were noted across a range of important health measures including mood, frailty, falls and reduced adverse reactions. This further supports deprescribing as a possible imperative to improve health outcomes in older adults.</p

Temperature dependence of the switching field distributions in all-perpendicular spin-valve nanopillars

We present temperature dependent switching measurements of the Co/Ni multilayered free element of 75 nm diameter spin-valve nanopillars. Angular dependent hysteresis measurements as well as switching field measurements taken at low temperature are in agreement with a model of thermal activation over a perpendicular anisotropy barrier. However, the statistics of switching (mean switching field and switching variance) from 20 K up to 400 K are in disagreement with a N\'{e}el-Brown model that assumes a temperature independent barrier height and anisotropy field. We introduce a modified N\'{e}el-Brown model thats fit the experimental data in which we take a $T^{3/2}$ dependence to the barrier height and the anisotropy field due to the temperature dependent magnetization and anisotropy energy.Comment: 5 pages, 4 figure