Interplay of rare-earth and transition-metal subsystems in Cu<inf>3</inf>Yb(SeO<inf>3</inf>)<inf>2</inf>O<inf>2</inf>Cl

©2017 American Physical Society We present the synthesis and the experimental and theoretical study of the new member of the francisite family, Cu 3 Yb(SeO 3 ) 2 O 2 Cl. The compound reaches an antiferromagnetic order at T N = 36.7 K and experiences first-order spin-reorientation transition to weakly ferromagnetic phase at T R = 8.7 K evidenced in specific heat C p and magnetic susceptibility χ measurements. Distinctly different magnetization loops in T < T R and T R < T < T N temperature ranges reflect the interplay of rare-earth and transition-metal subsystems. At low temperatures, the saturation magnetization M s ∼ 5.2 μ B is reached in pulsed magnetic-field measurements. The electron spin resonance data reveal the complicated character of the absorption line attributed to response from both copper and ytterbium ions. Critical broadening of the linewidth at the phase transitions points to quasi-two-dimensional character of the magnetic correlations. The spectroscopy of Yb 3+ ions evidences splitting of the lowest-energy Kramers doublet of 2 F 5 / 2 excited multiplet at T R < T < T N while the ground Kramers doublet splits only at T < T R . We describe the magnetic properties both above and below the spin-reorientation transition in the framework of a unified approach based on the mean-field approximation and crystal-field calculations

Symmetry breaking and circular photogalvanic effect in epitaxial CdxHg1-xTe films

We report on the observation of symmetry breaking and the circular photogalvanic effect in CdxHg1-xTe alloys. We demonstrate that irradiation of bulk epitaxial films with circularly polarized terahertz radiation leads to the circular photogalvanic effect (CPGE) yielding a photocurrent whose direction reverses upon switching the photon helicity. This effect is forbidden in bulk zinc-blende crystals by symmetry arguments; therefore, its observation indicates either the symmetry reduction of bulk material or that the photocurrent is excited in the topological surface states formed in a material with low cadmium concentration. We show that the bulk states play a crucial role because the CPGE was also clearly detected in samples with noninverted band structure. We suggest that strain is a reason for the symmetry reduction. We develop a theory of the CPGE showing that the photocurrent results from the quantum interference of different pathways contributing to the free-carrier absorption (Drude-like) of monochromatic radiation

Interplay of rare-earth and transition-metal subsystems in Cu<inf>3</inf>Yb(SeO<inf>3</inf>)<inf>2</inf>O<inf>2</inf>Cl

©2017 American Physical Society We present the synthesis and the experimental and theoretical study of the new member of the francisite family, Cu 3 Yb(SeO 3 ) 2 O 2 Cl. The compound reaches an antiferromagnetic order at T N = 36.7 K and experiences first-order spin-reorientation transition to weakly ferromagnetic phase at T R = 8.7 K evidenced in specific heat C p and magnetic susceptibility χ measurements. Distinctly different magnetization loops in T < T R and T R < T < T N temperature ranges reflect the interplay of rare-earth and transition-metal subsystems. At low temperatures, the saturation magnetization M s ∼ 5.2 μ B is reached in pulsed magnetic-field measurements. The electron spin resonance data reveal the complicated character of the absorption line attributed to response from both copper and ytterbium ions. Critical broadening of the linewidth at the phase transitions points to quasi-two-dimensional character of the magnetic correlations. The spectroscopy of Yb 3+ ions evidences splitting of the lowest-energy Kramers doublet of 2 F 5 / 2 excited multiplet at T R < T < T N while the ground Kramers doublet splits only at T < T R . We describe the magnetic properties both above and below the spin-reorientation transition in the framework of a unified approach based on the mean-field approximation and crystal-field calculations