We report on the observation of the hysteretic transition of a commensurate charge modulation in IrTe 2 from transport and scanning tunneling microscopy (STM) studies. Below the transition (T C ≈ 275 K on cooling), a q ¼ 1=5 charge modulation was observed, which is consistent with previous studies. Additional modulations [q n ¼ ð3n þ 2Þ −1 ] appear below a second transition at T S ≈ 180 K on cooling. The coexistence of various modulations persists up to T C on warming. The atomic structures of charge modulations and the temperature-dependent STM studies suggest that 1=5 modulation is a periodic soliton lattice that partially melts below T S on cooling. Our results provide compelling evidence that the ground state of IrTe 2 is a commensurate 1=6 charge modulation, which originates from the periodic dimerization of Te atoms visualized by atomically resolved STM images.

The authors fabricated Pb(Zr0.52Ti0.48)O3–NiFe2O4 composite films consisting of randomly dispersed NiFe2O4 nanoparticles in the Pb(Zr0.52Ti0.48)O3 matrix. The structural analysis revealed that the crystal axes of the NiFe2O4 nanoparticles are aligned with those of the ferroelectric matrix. The composite has good ferroelectric and magnetic properties. The authors measured the transverse and longitudinal components of the magnetoelectric voltage coefficient, which supports the postulate that the magnetoelectric effect comes from direct stress coupling between magnetostrictive NiFe2O4 and piezoelectric Pb(Zr0.52Ti0.48)O3 grains.

We have fabricated c-axis Josephson junctions on single crystals of Ba1-xKxFe2As2 by using Pb as the counterelectrode in two geometries, planar and point contact. Junctions in both geometries show resistively shunted junction I-V curves below the T{C} of the counterelectrode. Microwave induced steps were observed in the I-V curves, and the critical currents are suppressed with an in-plane magnetic field with well-defined modulation periods indicating that the Josephson current is flowing in a manner consistent with the small to intermediate sized junction limit. I{C}R{N} products of up to 0.3 mV have been observed in these junctions at 4.2 K. The observation of Josephson coupling along the c axis between Ba1-xKxFe2As2 and a conventional superconductor suggests the existence of an s-wave symmetry in this class of iron pnictide superconductors.

The authors investigated the magnetic and ferroelectric properties of hexagonally grown HoMnO3 thin films. The magnetic measurements revealed bulklike magnetic phase transitions with an additional spin-glass-like behavior feature below the Néel temperature. The ferroelectricity in the films was distinctly different from the suggested bulk behavior. Below 40K, the HoMnO3 films showed typical ferroelectric character: their remnant polarization and coercive field values at 20K were 3.7μC∕cm2 and 0.69MV∕cm. Above 40K, however, the films exhibited an unusual antiferroelectriclike behavior, with more pronounced features appearing at higher temperatures. These intriguing physical properties make HoMnO3 films a potential candidate material for numerous future applications.

We have observed the Josephson effect in junctions formed between single crystals of SrFe 1.74 Co 0.26 As 2 and Ba 0.23 K 0.77 Fe 2 As 2 . I-V curves showed resistively-shunted junction characteristics, and the ac Josephson effect was observed under microwave irradiation.

No abstract

No abstract

We report extraordinarily large magnetic hysteresis loops in the iridates Sr 3 NiIrO 5 and Sr 3 CoIrO 6 . We find coercive magnetic fields of up to 55 T with switched magnetic moments ≈1 μ B per formula unit in Sr 3 NiIrO 6 and coercive fields of up to 52 T with switched moments ≈3 μ B per formula unit in Sr 3 CoIrO 6 . We propose that the magnetic hysteresis involves the field-induced evolution of quasi-one-dimensional chains in a frustrated triangular configuration. The striking magnetic behavior is likely to be linked to the unusual spin-orbit-entangled local state of the Ir 4+ ion and its potential for anisotropic exchange interactions.