We report on the high-pressure syntheses and detailed characterizations of two effective pseudospin S-1/2 XY pyrochlores Er 2 Pt 2 O 7 andYb 2 Pt 2 O 7 via X-ray/neutron powder diffraction, dc and ac magnetic susceptibility, and specific-heat measurements down to 70 mK. We found that both compounds undergo long-range magnetic transition at T N,C ≈ 0.3 K, which are ascribed to an antiferromagnetic-and ferromagnetic-type order for Er 2 Pt 2 O 7 and Yb 2 Pt 2 O 7 , respectively, based on the field dependence of their transition temperature as well as the systematic comparisons with other similar pyrochlores R 2 B 2 O 7 (R = Er, Yb; B = Sn, Ti, Ge). The observed T N of Er 2 Pt 2 O 7 is much lower than that expected from the relationship of T N versus the ionic radius of B 4+ derived from the series of Er 2 B 2 O 7 , while the T C of Yb 2 Pt 2 O 7 is the highest among the series of ferromagnetic Yb 2 B 2 O 7 (B = Sn, Pt, Ti). Given the monotonic variation of the lattice constant as a function of the B-cation size across these two series of R 2 B 2 O 7 (R = Er, Yb), the observed anomalous values of T N,C in the Pt-based XY pyrochlores imply another important factor beyond the nearest-neighbor R-R distance is playing a role. In light of the anisotropic exchange interactions J ex = {J zz , J ± , J ±± , J z± } for the S-1/2 XY pyrochlores, we have rationalized these observations by considering a weakened (enhanced) antiferromagnetic planar J ± (ferromagnetic Ising-like J zz ) due to strong Pt 5d-O 2p hybridization within the plane perpendicular to the local [111] direction.

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Light-field imaging is a crucial and straightforward way of measuring and analyzing surrounding light worlds. In this paper, a dual-polarized light-field imaging micro-system based on a twisted nematic liquid-crystal microlens array (TN-LCMLA) for direct three-dimensional (3D) observation is fabricated and demonstrated. The prototyped camera has been constructed by integrating a TN-LCMLA with a common CMOS sensor array. By switching the working state of the TN-LCMLA, two orthogonally polarized light-field images can be remapped through the functioned imaging sensors. The imaging micro-system in conjunction with the electric-optical microstructure can be used to perform polarization and light-field imaging, simultaneously. Compared with conventional plenoptic cameras using liquid-crystal microlens array, the polarization-independent light-field images with a high image quality can be obtained in the arbitrary polarization state selected. We experimentally demonstrate characters including a relatively wide operation range in the manipulation of incident beams and the multiple imaging modes, such as conventional two-dimensional imaging, light-field imaging, and polarization imaging. Considering the obvious features of the TN-LCMLA, such as very low power consumption, providing multiple imaging modes mentioned, simple and low-cost manufacturing, the imaging micro-system integrated with this kind of liquid-crystal microstructure driven electrically presents the potential capability of directly observing a 3D object in typical scattering media.