Interplay between spin-density wave and 3d local moments with random exchange in a molecular conductor

Article

关键词: ONE-DIMENSIONAL CONDUCTOR;    MAGNETIC-PROPERTIES;    NEGATIVE MAGNETORESISTANCE;    X-RAY;    ANISOTROPY;    MEMORY;    SUPERCONDUCTIVITY;    ANTIFERROMAGNETS;    (TMTSF)(2)PF6;    HYSTERESIS;   

DOI  :  10.1103/PhysRevB.93.075124

来源: SCIE

【 摘 要 】

We present the results of high-pressure transport measurements on the anion-mixed molecular conductors (DIETSe)(2)MBr2Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene; M = Fe, Ga]. They undergo a metal-insulator (M-I) transition below 9 K at ambient pressure, which is suppressed by applying pressure, indicating a spin-density-wave (SDW) transition caused by a nesting instability of the quasi-one-dimensional (Q1D) Fermi surface, as observed in the parent compounds (DIETSe)(2)MCl4 (M = Fe, Ga). In the metallic state, the existence of the Q1D Fermi surface is confirmed by observing the Lebed resonance. The critical pressures of the SDW, Pc, of the MBr2Cl2 (M = Fe, Ga) salts are significantly lower than those of the the MCl4 (M = Fe, Ga) salts, suggesting chemical pressure effects. Above P-c, field-induced SDW transitions appear, as evidenced by kink structures in the magnetoresistance (MR) in both salts. The FeBr2Cl2 salt also shows antiferromagnetic (AF) ordering of d spins at 4 K, below which significant spin-charge coupling is observed. A large positive MR change up to 150% appears above the spin-flop field at high pressure. At low pressure, in particular below P-c, a dip or kink structure appears in MR at the spin-flop field, which shows unconventionally large hysteresis at low temperature (T < 1 K). The hysteresis region clearly decreases with increasing pressure towards P-c, strongly indicating that the coexisting SDW plays an important role in the enhancement of magnetic hysteresis besides the random exchange interaction.

【 授权许可】

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