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)