Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound 
Rb4O6

Cs2SbCl6 is known as a typical mixed-valence compound. It crystallizes into a tetragonal space group I41/amd and contains two different complex anions, Sb(III)Cl3-6 and Sb(V)Cl-6 . The dark blue color of this compound has been considered to originate from a charge transfer between the above two anions. In order to study the electronic structure of these complex anions and the existence of charge transfer between them we measured the 121Sb NMR spectrum and carried out molecular orbital calculations on the electronic states of these anions. The 121Sb NMR spectrum consists of two peaks at 0 and 30 kHz which can be assigned to the central transition of 121Sb in Sb(V)Cl-6 and Sb(III)Cl3-6 , respectively. The line shape analyses of the spectra led to nuclear quadrupole coupling constants of nearly zero for Sb(V)Cl-6 and 4.9 ± 0.5 MHz for Sb(III)Cl3-6 at room temperature. The quadrupole coupling constant of 121Sb(III) decreases steadily on heating. The calculations of the electronic ground state energies of both anions were calculated by the MS-Xα molecular orbital method. The calculated charge-transfer band from the A1g state of Sb(III)Cl3-6 to the A1g state of Sb(V)Cl-6 appears at 610 nm and can account for the experimental electronic spectrum, the calculated quadrupole coupling constant in Sb(III)Cl3-6 however is far larger than the experimental one. The contribution of the charge-transferred state to the ground state is negligible and so the temperature dependence of the quadrupole coupling constant of 121Sb(III) is attributed to an anisotropic thermal expansion of the compound.

Download Full-text

Possible 4 f 7 5 d 1 Ground State of Gd Impurities in the Mixed-Valence Compound SmB 6 , Observed with Electron Spin Resonance

EPL (Europhysics Letters) ◽

10.1209/0295-5075/11/8/016 ◽

1990 ◽

Vol 11 (8) ◽

pp. 791-796 ◽

Cited By ~ 12

Author(s):

G Wiese ◽

H Schäffer ◽

B Elschner

Keyword(s):

Electron Spin Resonance ◽

Electron Spin ◽

Ground State ◽

Mixed Valence ◽

Spin Resonance ◽

Mixed Valence Compound

Download Full-text

Imaging the formation and surface phase separation of the CE phase

npj Quantum Materials ◽

10.1038/s41535-021-00353-2 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Haibiao Zhou ◽

Qiyuan Feng ◽

Yubin Hou ◽

Masao Nakamura ◽

Yoshinori Tokura ◽

...

Keyword(s):

Magnetic Field ◽

Phase Transitions ◽

Charge Ordering ◽

Zero Magnetic Field ◽

Ferromagnetic Phase ◽

Emergent Properties ◽

Orbital Ordering ◽

Strong Electron ◽

Antiferromagnetic Correlation ◽

Ordering Transitions

AbstractThe CE phase is an extraordinary phase exhibiting the simultaneous spin, charge, and orbital ordering due to strong electron correlation. It is an ideal platform to investigate the role of the multiple orderings in the phase transitions and discover emergent properties. Here, we use a cryogenic high-field magnetic force microscope to image the phase transitions and properties of the CE phase in a Pr0.5Ca0.5MnO3 thin film. In a high magnetic field, we observed a clear suppression of magnetic susceptibility at the charge-ordering insulator transition temperature (TCOI), whereas, at the Néel temperature (TN), no significant change is observed. This observation favors the scenario of strong antiferromagnetic correlation developed below TCOI but raises questions about the Zener polaron paramagnetic phase picture. Besides, we discoverd a phase-separated surface state in the CE phase regime. Ferromagnetic phase domains residing at the surface already exist in zero magnetic field and show ultra-high magnetic anisotropy. Our results provide microscopic insights into the unconventional spin- and charge-ordering transitions and revealed essential attributes of the CE phase, highlighting unusual behaviors when multiple electronic orderings are involved.

Download Full-text