800 research outputs found
Field- and pressure-induced phases in SrRuO: A spectroscopic investigation
We have investigated the magnetic-field- and pressure-induced structural and
magnetic phases of the triple-layer ruthenate - SrRuO.
Magnetic-field-induced changes in the phonon spectra reveal dramatic
spin-reorientation transitions and strong magneto-elastic coupling in this
material. Additionally, pressure-dependent Raman measurements at different
temperatures reveal an anomalous negative Gruneisen-parameter associated with
the B mode ( 380 cm) at low temperatures (T 75K), which
can be explained consistently with the field dependent Raman data.Comment: 5 pages, 4 figures final version published in PRL 96, 067004 (2006
Discourse and identity in a corpus of lesbian erotica
This article uses corpus linguistic methodologies to explore representations of lesbian desires and identities in a corpus of lesbian erotica from the 1980s and 1990s. We provide a critical examination of the ways in which “lesbian gender,” power, and desire are represented, (re-)produced, and enacted, often in ways that challenge hegemonic discourses of gender and sexuality. By examining word frequencies and collocations, we critically analyze some of the themes, processes, and patterns of representation in the texts. Although rooted in linguistics, we hope this article provides an accessible, interdisciplinary, and timely contribution toward developing understandings of discursive practices surrounding gender and sexuality
Quantized spin excitations in a ferromagnetic microstrip from microwave photovoltage measurements
Quantized spin excitations in a single ferromagnetic microstrip have been
measured using the microwave photovoltage technique. Several kinds of spin wave
modes due to different contributions of the dipole-dipole and the exchange
interactions are observed. Among them are a series of distinct dipole-exchange
spin wave modes, which allow us to determine precisely the subtle spin boundary
condition. A comprehensive picture for quantized spin excitations in a
ferromagnet with finite size is thereby established. The dispersions of the
quantized spin wave modes have two different branches separated by the
saturation magnetization.Comment: 4 pages, 3 figure
Controlled switching of intrinsic localized modes in a 1-D antiferromagnet
Nearly steady-state locked intrinsic localized modes (ILMs) in the quasi-1d
antiferromagnet (C2H5NH3)2CuCl4 are detected via four-wave mixing emission or
the uniform mode absorption. Exploiting the long-time stability of these locked
ILMs, repeatable nonlinear switching is observed by varying the sample
temperature, and localized modes with various amplitudes are created by
modulation of the microwave driver power. This steady-state ILM locking
technique could be used to produce energy localization in other atomic
lattices.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett. v.2 :
clarifications of text and figures in response to comment
Magnetization Reversal in Elongated Fe Nanoparticles
Magnetization reversal of individual, isolated high-aspect-ratio Fe
nanoparticles with diameters comparable to the magnetic exchange length is
studied by high-sensitivity submicron Hall magnetometry. For a Fe nanoparticle
with diameter of 5 nm, the magnetization reversal is found to be an incoherent
process with localized nucleation assisted by thermal activation, even though
the particle has a single-domain static state. For a larger elongated Fe
nanoparticle with a diameter greater than 10 nm, the inhomogeneous magnetic
structure of the particle plays important role in the reversal process.Comment: 6 pages, 6 figures, to appear in Phys. Rev. B (2005
Parity-odd multipoles, magnetic charges and chirality in haematite (alfa-Fe2O3)
Collinear and canted magnetic motifs in haematite were investigated by
Kokubun et al. (2008) using x-ray Bragg diffraction magnified at the iron
K-edge, and analyses of observations led to various potentially interesting
conclusions. We demonstrate that the reported analyses for both non-resonant
and resonant magnetic diffraction at low energies near the absorption K-edge
are not appropriate. In its place, we apply a radically different formulation,
thoroughly tried and tested, that incorporates all magnetic contributions to
resonant x-ray diffraction allowed by the established chemical and magnetic
structures. Essential to a correct formulation of diffraction by a magnetic
crystal with resonant ions at sites that are not centres of inversion symmetry
are parity-odd atomic multipoles, time-even (polar) and time-odd
(magneto-electric), that arise from enhancement by the electric-dipole (E1) -
electric-quadrupole (E2) event. Analyses of azimuthal-angle scans on two
space-group forbidden reflections, hexagonal (0, 0, 3)h and (0, 0, 9)h,
collected by Kokubun et al. above and below the Morin temperature (TM = 250K),
allow us to obtain good estimates of contributing polar and magneto-electric
multipoles, including the iron anapole. We show, beyond reasonable doubt, that
available data are inconsistent with parity-even events only (E1-E1 and E2-
E2). For future experiments, we show that chiral states of haematite couple to
circular polarization and differentiate E1-E2 and E2-E2 events, while the
collinear motif supports magnetic charges
Group experiences of cognitive stimulation therapy (CST) in Tanzania: a qualitative study
BACKGROUND: Tanzania is a low-income country in which medication for dementia is largely unavailable. Cognitive Stimulation Therapy (CST) is a group-based psychological treatment for people with dementia (PwD), shown to improve cognition and quality of life (QoL). It has previously been culturally adapted and piloted in Tanzania, shown to produce similar outcomes. UK research into CST suggests processes inherent to the group nature are key to its success. This study sought to identify group processes within CST in Tanzania and understand their impact on CST principles and outcomes. METHODS: Data collection took place in rural Hai District, through qualitative semi-structured interviews. Sixteen PwD and four facilitators were recruited through convenience sampling and interviewed about their experiences of CST. Interviews were audio-recorded, translated, transcribed and analysed by thematic analysis. RESULTS: Two main themes emerged: 'Positive group experiences' and 'Negative group experiences'. From this, a number of group processes were identified, such as helping behaviours and feeling understood by the group. Positive processes supported CST principles and participant improvement. Facilitators were influential over group dynamics. The group processes identified impacted CST principles and treatment outcomes. CONCLUSIONS: This is the first study on group mechanisms of CST in Tanzania. It provides deeper insight into participants' experiences of CST, thus identifying specific processes underlying the quantitatively measured positive outcomes of CST in Tanzania by previous studies. It also reveals further cultural barriers to implementation, enabling amendments for optimization of treatment efficacy
Detection of Temper Embrittlement in Steel by Magnetoacoustic Emssion Technique
A bulk ferromagnet possesses two types of domain walls: 180° and non-180° [1]. In the case of iron-like ferromagnets, the latter type of walls are 90° domain walls. As a result of the magnetoelastic interaction, unit cells of a ferromagnet deform slightly in a way that is unique to particular types of domains [2]. Such a spontaneous deformation, called magnetostriction, causes local lattice strains at domain walls with the strain fields being particularly strong for 90° domain walls [3]. The motion of the 90° domain walls is followed by a redistribution of local lattice strain fields. Elastic energy is being released by this process and propagates through material as acoustic waves. Acoustic emission (AE) generated due to magnetic domain wall motion is thus defined as magnetoacoustic emission (MAE)
Anisotropy effects on the magnetic excitations of a ferromagnetic monolayer below and above the Curie temperature
The field-driven reorientation transition of an anisotropic ferromagnetic
monolayer is studied within the context of a finite-temperature Green's
function theory. The equilibrium state and the field dependence of the magnon
energy gap are calculated for static magnetic field applied in plane
along an easy or a hard axis. In the latter case, the in-plane reorientation of
the magnetization is shown to be continuous at T=0, in agreement with free spin
wave theory, and discontinuous at finite temperature , in contrast with
the prediction of mean field theory. The discontinuity in the orientation angle
creates a jump in the magnon energy gap, and it is the reason why, for ,
the energy does not go to zero at the reorientation field. Above the Curie
temperature , the magnon energy gap vanishes for H=0 both in the
easy and in the hard case. As is increased, the gap is found to increase
almost linearly with , but with different slopes depending on the field
orientation. In particular, the slope is smaller when is along the hard
axis. Such a magnetic anisotropy of the spin-wave energies is shown to persist
well above ().Comment: Final version accepted for publication in Physical Review B (with
three figures
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