Stabilization of metastable expanded face-centered-tetragonal manganese

The structural and magnetic properties of Mn prepd. on single cryst. face-centered-tetragonal (fct) Co(001) were investigated. Mn grows coherently up to at least 50 monolayers (ML) and adopts a metastable expanded fct(001) phase [c/a=1.055(5)]. This new fct-Mn phase was recently predicted theor. by Hafner and Spisak [Phys. Rev. B 72, 144420 (2005)]. Studies of magnetic Mn/Co interface exchange interactions prove the room temp. antiferromagnetic state for thicknesses above 2.5 ML. The magnetic anisotropy of the thin Mn is high enough to induce a significant exchange anisotropy for Mn thicknesses as low as 6 ML. The potential of fct-Mn to become a novel model system for systematic studies on the exchange interactions at antiferromagnet/ferromagnet interfaces is discussed. [on SciFinder (R)

Hyperfine field distribution in the Heusler compound Co2FeAl probed by 59Co nuclear magnetic resonance

The Heusler compound Co2FeAl is reported to occur in various structures ranging from the completely ordered L21 to the completely disordered A2 structure type. In this work, we use spin echo nuclear magnetic resonance (NMR) to probe the local structure of Co2FeAl bulk samples. The study of Co2FeAl bulk samples provides the unique possibility to verify the intrinsic generic structural properties. The 59Co NMR measurements reveal a distribution of Fe and Al not only in the first neighbouring shells of the 59Co nuclei but also in more distant shells. The analysis of 59Co NMR main resonance lines with an underlying sub-structure confirms that the local structure of the as-cast Co2FeAl bulk samples consists of a B2 type structure with contributions of the L21 type structure of about 10%. The observed sub-lines, which are attributed to a distribution of Fe and Al atoms in more distant shells, were previously not resolved in NMR spectra of Co2FeAl thin films, pointing to better long range order in bulk material than in thin films. We also show that the individual contributions of the structure types can be influenced by annealing

Origin of biquadratic exchange in Fe/Si/Fe

The thickness and temperature dependences of the interlayer exchange coupling in well-defined molecular beam epitaxy-grown Fe/Si/Fe sandwich structures have been studied. The biquadratic coupling shows a strong temperature dependence in contrast to the bilinear coupling. Both depend exponentially on thickness. These observations can be well understood in the framework of Slonczewski's loose spins model [J. Appl. Phys. 73, 5957 (1993)]. No bilinear contribution of the loose spins to the coupling was observed

Biquadratic interlayer exchange coupling in epitaxial Fe/Si/Fe

\u3cp\u3eWe have studied the biquadratic exchange coupling in epitaxially grown Fe/Si/Fe. The temperature and thickness dependence of the biquadratic coupling strength were determined unambiguously by fitting the easy- and hard-axis magneto-optical Kerr effect loops. The origin of the biquadratic coupling can be fully understood in terms of Slonczewski's loose spins mechanism.\u3c/p\u3

Ways of ‘Being With’: Caring for Dying patients at the Height of the Covid-19 Pandemic

Palliative care professionals often speak of the importance of forming meaningful relationships with patients and their families. Trust and rapport, usually established over extended periods of time through face-to-face interactions, and a ‘gentle honesty’ regarding end-of-life and death are key aspects of developing a sense of intimacy with people who are approaching the end of their lives. A fundamental feature of this intimacy is conveying a sense of ‘being with’ a patient. However, these ways of working were greatly challenged by the impact of COVID-19. This article explores how intimacy both was and was not established at the height of the pandemic, and it describes the extent to which shared concerns functioned as a new means to create a sense of a common experience

Laser-induced magnetization dynamics in Co/IrMn exchange coupled bilayers

The response of a ferromagnet/antiferromagnet exchange coupled bilayer to femtosecond laser heating is studied by means of pump-probe time-resolved magneto-optical Kerr effect (TR-MOKE) in the polar geometry on a Co (10 nm)/IrMn (0-15 nm wedge) sample. When an external field is applied in the film plane, perpendicular to the exchange bias direction, a damped precessional motion of the ferromagnetic spins can be triggered by laser excitation. We observe that the exchange bias field HEB,dyn, extd. from the TR data, systematically differs from the value HEB,st, obtained by static MOKE loop measurements, for thin

Controlled domain-wall injection in perpendicularly magnetized strips

For applications of domain wall (DW) motion in magnetic devices, it is vital to control the creation and position of the DW. We use Ga+ irradiation of Pt/Co/Pt strips to locally change the perpendicular magnetic anisotropy. This allows us to controllably inject DWs into a device at a tunable field. The observed initial linear decrease and subsequent increase in the DW injection field upon increasing irradiation dose are explained by micromagnetic simulations and an analytical one-dimensional model

Role of the barrier in spin-dependent tunneling addressed with superconductor spectroscopy

To establish the role of the barrier material in spin-polarized tunneling, the authors directly measure the sign and magnitude of the tunneling spin polarization in Al/barrier/ferromagnet junctions with different barriers using the Zeeman-split superconducting d. of states of the Al electrode. It is shown that clear Zeeman splitting is difficult to obtain with heavy metal oxide barriers, such as HfOx and TaOx, due to a large spin-orbit scattering rate most likely induced by the heavy atoms at the Al/barrier interface. Junctions with MgO barriers, however, show clear Zeeman splitting and a tunneling spin polarization of +30% with both Co and Fe as the top electrode, a no. which significantly differs from +40% found for our AlOx junctions. We claim that this barrier dependence originates from the electronic structure of the barrier/ferromagnet interface. The pos. tunneling polarization is consistent with the presumption that due to the absence of d orbitals in the MgO barrier, tunneling is dominated by electrons with s character. [on SciFinder (R)

Tunable magnetic domain wall oscillator at an anisotropy boundary

We propose a magnetic domain wall (DW) oscillator scheme, in which a low dc current excites gigahertz angular precession of a DW at a fixed position. The scheme consists of a DW pinned at a magnetic anisotropy step in a perpendicularly magnetized nanostrip. The frequency is tuned by the current flowing through the strip. A perpendicular external field tunes the critical current density needed for precession, providing great experimental flexibility. We investigate this system using a simple one-dimensional model and full micromagnetic calculations. This oscillating nanomagnet is relatively easy to fabricate and could find application in future nanoscale microwave sources. © 2011 American Institute of Physics