99 research outputs found
Field induced phase transitions in the helimagnet Ba2CuGe2O7
We present a theoretical study of the two-dimensional spiral antiferromagnet
Ba2CuGe2O7 in the presence of an external magnetic field. We employ a suitable
nonlinear sigma model to calculate the T=0 phase diagram and the associated
low-energy spin dynamics for arbitrary canted fields, in general agreement with
experiment. In particular, when the field is applied parallel to the c axis, a
previously anticipated Dzyaloshinskii-type incommensurate-to-commensurate phase
transition is actually mediated by an intermediate phase, in agreement with our
earlier theoretical prediction confirmed by the recent observation of the
so-called double-k structure. The sudden pi/2 rotations of the magnetic
structures observed in experiment are accounted for by a weakly broken U(1)
symmetry of our model. Finally, our analysis suggests a nonzero
weak-ferromagnetic component in the underlying Dzyaloshinskii-Moriya
anisotropy, which is important for quantitative agreement with experiment.Comment: 17 pages, 14 figures. Corrected typos in the abstrac
A map for successful CCNE accreditation
The purpose of this article is to provide nurse educators with recommendations on how to develop the needed structures and processes that lead to accreditation success. We provide a comprehensive list of 28 recommendations, a timeline for completion of tasks, and specific information on how to document the achievement of the four CCNE Standards. The first two recommendations deal with two vital structures that comprise a well-functioning program: an effective committee structure and a robust evaluation plan. Recommendations 3 to 12 concern the process steps for preparing for an accreditation visit and are aligned with a timeline for completion. The remaining recommendations address how to document compliance with each CCNE standard
Magnetic structures and reorientation transitions in noncentrosymmetric uniaxial antiferromagnets
A phenomenological theory of magnetic states in noncentrosymmetric tetragonal
antiferromagnets is developed, which has to include homogeneous and
inhomogeneous terms (Lifshitz-invariants) derived from Dzyaloshinskii-Moriya
couplings. Magnetic properties of this class of antiferromagnets with low
crystal symmetry are discussed in relation to its first known members, the
recently detected compounds Ba2CuGe2O7 and K2V3O8. Crystallographic symmetry
and magnetic ordering in these systems allow the simultaneous occurrence of
chiral inhomogeneous magnetic structures and weak ferromagnetism. New types of
incommensurate magnetic structures are possible, namely, chiral helices with
rotation of staggered magnetization and oscillations of the total
magnetization. Field-induced reorientation transitions into modulated states
have been studied and corresponding phase diagrams are constructed. Structures
of magnetic defects (domain-walls and vortices) are discussed. In particular,
vortices, i.e. localized non-singular line defects, are stabilized by the
inhomogeneous Dzyaloshinskii-Moriya interactions in uniaxial noncentrosymmetric
antiferromagnets.Comment: 18 pages RevTeX4, 13 figure
Piezoresponse force microscopy and electron backscattering diffraction of 90° ferroelectric twins in BaTiO3 positive temperature coefficient (PTC) thermistors
The authors acknowledge funding from the European Union's Horizon 2020 research and innovation program, OYSTER (Open characterisation and modelling environment to drive innovation in advanced nanoarchitectured and bio-inspired hard/soft interfaces) under grant agreement No 760827, Enterprise Ireland, Innovation Partnership Programme (Project No: IP/2013/0281), Irish Research Council postgraduate scholarship and Higher Education Authority (HEA)
- …