Magnetic frustration and disorder are key ingredients to prevent the onset of magnetic order. In the disordered hexagonal double perovskite BaTi 1/2 Mn 1/2 O3, Mn 4+ cations, with S = 3/2 spins, can either form highly correlated states of magnetic trimers or dimers or remain as weakly interacting orphan spins. At low temperature (T ), the dimer response is negligible, and magnetism is dominated by the trimers and orphans. To explore the role of magnetic frustration, disorder and possibly of quantum fluctuations, the low-T magnetic properties of the remaining magnetic degrees of freedom of BaTi 1/2 Mn 1/2 O3 are investigated. Heat-capacity data and magnetic susceptibility display no evidence for a phase transition to a magnetically ordered phase but indicate the formation of a correlated spin state. The low-temperature spin dynamics of this state is then explored by µSR experiments. The zero field µ + relaxation rate data show no static magnetism down to T = 19 mK and longitudinal field experiments support as well that dynamic magnetism persists at low T . Our results are interpreted in terms of a spin glass state which stems from a disordered lattice of orphans spins and trimers. A spin liquid state in BaTi 1/2 Mn 1/2 O3, however, is not excluded and is also discussed.

We present the proof of concept of a general model that uses the tissue sample transmittance as input to estimate the depth‐resolved attenuation coefficient of tissue samples using optical coherence tomography (OCT). This method allows us to obtain an image of tissue optical properties instead of intensity contrast, guiding diagnosis and tissues differentiation, extending its application from thick to thin samples. The performance of our method was simulated and tested with the assistance of a home built single‐layered and multilayered phantoms (~100 μm each layer) with known attenuation coefficient on the range of 0.9 to 2.32 mm−1. It is shown that the estimated depth‐resolved attenuation coefficient recovers the reference values, measured by using an integrating sphere followed by the inverse adding doubling processing technique. That was corroborated for all situations when the correct transmittance value is used with an average difference of 7%. Finally, we applied the proposed method to estimate the depth‐resolved attenuation coefficient for a thin biological sample, demonstrating the ability of our method on real OCT images.

No abstract

No abstract

No abstract