A novel superconductor with insulating magnetic ground state
A novel superconductor with insulating magnetic ground state
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一种具有绝缘磁基态的新型超导体
DOI：
10.1016/s0010-8545(99)00129-0
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发表时间：
1999
影响因子：
20.6
通讯作者：
P. Cassoux
中科院分区：
文献类型：
--
作者：
H. Kobayashi;A. Sato;Hisashi Tanaka;A. Kobayashi;P. Cassoux
具有混合阴离子的BETS导体λ-BETS 2FexGa 1 − xCl 4（BETS=双（亚乙基二硫代）四硒富瓦烯）在环境压力下在x=0.43附近表现出前所未有的超导体到绝缘体（SC-I）转变。磁化率在Tc（~ 4.2 K）处的大幅下降和在TSC-1（~ 3.2 K）处的恢复清楚地表明，这种SC-1转变反映了晶体的固有性质。在4 K时，系统处于超导状态，交流磁化率的大小（ε −40 emu mol−1）给出了约75%的迈斯纳体积分数。磁化强度的各向异性和场依赖性低于TSC-I表明绝缘基态是反铁磁的，易磁化轴平行于c。对λ-BETS 2FexGa 1 − xCl 4的系统性研究表明，该体系在x> xc 1（λ = 0.5）时发生MI跃迁，在x<xc 2（λ = 0.35）时发生SC跃迁，在xc 2 <x<xc 1时发生SC-I跃迁。在λ-BETS 2FexGa 1 − xCl 4（x = 0.55）中也观察到了SC-I跃迁，在环境压力下表现出金属-绝缘体（M-I）跃迁。高压电阻率测量表明，在λ-BETS_2Fe_（0.7）Ga_（0.3）Cl_4中存在超导转变。基于这些电阻率测量，获得了λ-BETS 2FexGa 1 − xCl 4的初步P-T-x相图。λ-BETS 2FexGa 1 − xCl 4（x=1.0，0.7，0.55和0.43）的磁化率的各向异性和场依赖性表明了绝缘基态的特征π-d耦合反铁磁结构。含Br的系统λ-BETS 2FexGa 1 − xBrCl 3在常压下是半导体。但λ-BETS 2FexGa 1 −xBrCl（x=0.5）在2kbar下表现出SC-I跃迁（Tc=7 K和TSC-I=3 K）。而λ-BETS 2FexGa 1 −xBrCl（x = 0.1-0.2）在1.5 kbar附近显示出SC-M（金属）跃迁。令人惊讶的是，λ-BETS 2FexGa 1 −xBrCl（x ≤ 0.1）的磁化率显示了在环境压力下4 K附近稀释的Fe 3+自旋的反铁磁有序。低于TSC-最小值的金属态的恢复似乎与Fe自旋的磁有序有关。
The BETS conductor with mixed anions, λ-BETS2FexGa1−xCl4(BETS=bis(ethylenedithio)tetraselenafulvalene) exhibited an unprecedented superconductor-to-insulator (SC–I) transition around x=0.43 at ambient pressure. The large drop in magnetic susceptibility at Tc(≈4.2 K) and its recovery at TSC–I(≈3.2 K) clearly showed that this SC–I transition reflects an intrinsic nature of the crystal. The magnitude of ac susceptibility (≈−40 emu mol−1) at 4 K, where the system is in the superconducting state, gave the Meissner volume fraction of about 75%. The anisotropy and field dependence of magnetization below TSC–Iindicate the insulating ground state to be antiferromagnetic with easy axis parallel to c. The systematic examination of the resistivities of λ-BETS2FexGa1−xCl4showed that the system undergoes a MI transition at x>xc1(≈0.5), SC transition at x<xc2(≈0.35) and SC–I transition at xc2<x<xc1. The SC–I transition was also observed in λ-BETS2FexGa1−xCl4(x≈0.55) at 1 kbar, which exhibited a metal–insulator (M–I) transition at ambient pressure. The high-pressure resistivity measurements revealed a superconducting transition in λ-BETS2Fe0.7Ga0.3Cl4. Based on these resistivity measurements, the preliminary P-T-x phase diagram of λ-BETS2FexGa1−xCl4was obtained. The anisotropy and field dependence of the susceptibilities of λ-BETS2FexGa1−xCl4(x=1.0, 0.7, 0.55 and 0.43) suggested the characteristic π-d coupled antiferromagnetic structure of the insulating ground state. The Br-containing system, λ-BETS2FexGa1−xBrCl3was semiconducting at ambient pressure. But λ-BETS2FexGa1−xBrCl (x=0.5) exhibited a SC–I transition (Tc=7 K and TSC–I=3 K) at 2 kbar. While λ-BETS2FexGa1−xBrCl (x≈0.1–0.2) showed a SC–M (metal) transition around 1.5 kbar. It was quite surprising that the susceptibility of λ-BETS2FexGa1−xBrCl (x≈0.1) showed the antiferromagnetic ordering of the diluted Fe3+spins around 4 K at ambient pressure. The recovery of the metallic state below TSC–Min this system seems to be connected with the magnetic ordering of Fe spins.
影响因子：
15
作者：
Kobayashi, H;Tomita, H;Cassoux, P
通讯作者：
Cassoux, P