High Magnetic Field ESR in S = 1 Skew Chain Antiferromagnet Ni2V2O7 Single Crystal

We report electron spin resonance (ESR) in S = 1 skew chain antiferromagnet Ni2V2O7, which exhibits a spin-flop transition and a well-defined 1/2 magnetization plateau. The antiferromagnetic (AFM) ordering at TN = 7 K can be reflected by the temperature-dependent ESR spectra at low frequency for the easy axis. At 2 K, at the spin-flop transition fields along the easy a and b axes, anomalies are observed from the frequency‒field relationship. However, these modes cannot be understood by the conventional two-sublattice AFM resonance theory with uniaxial anisotropy. For the easy b axis, an unusual resonance mode is observed and its resonance field increases with decreasing frequency. This ESR mode becomes softening at ~8 T, corresponding to the onset of the 1/2 magnetization plateau.

Electric field computation and measurements in the electroporation of inhomogeneous samples

In clinical treatments of a class of tumors,e.g. skin tumors, the drug uptake of tumor tissue is helped by means of a pulsed electric field, which permeabilizes the cell membranes. This technique, which is called electroporation, exploits the conductivity of the tissues: however, the tumor tissue could be characterized by inhomogeneous areas, eventually causing a non-uniform distribution of current. In this paper, the authors propose a field model to predict the effect of tissue inhomogeneity, which can affect the current density distribution. In particular, finite-element simulations, considering non-linear conductivity against field relationship, are developed. Measurements on a set of samples subject to controlled inhomogeneity make it possible to assess the numerical model in view of identifying the equivalent resistance between pairs of electrodes.