Magnetic properties of λ-BETS2(FexGa1−x)Cl4 exhibiting a superconductor-to-insulator transition (0.35<x<0.5)

Abstract

The crystal of λ-(BETS)2(FexGa1−x)Cl4 with x≈0.45 undergoes successive superconducting and superconductor-to-insulator transitions around liquid helium temperature. The large diamagnetic susceptibility (≈-35 emu/mol at 4 K) observed in the superconducting phase of the system with x≈0.47, which exhibits a superconducting transition at 4.3 K and superconductor-to-insulator transition at 3.7 K, can be regarded as evidence for the bulk nature of the superconductor-to-insulator transition. The anisotropy of the susceptibility and spin-flop behavior indicate that the system takes a π-d coupled antiferromagnetic insulating ground state, which is essentially the same as that of λ-(BETS)2FeCl4 exhibiting a coupled metal-insulator and antiferromagnetic transition at 8.5 K. The easy axis is parallel to the c direction. Unlike the Ga-rich system (x<0.35) with superconducting ground state, the Fe-rich system such as λ-(BETS)2(Fe0.7Ga0.3)Cl4 shows a metal-insulator transition at ambient pressure. At high pressure, however, the π and d electrons tend to be independent of each other and the system takes a superconducting ground state.

Source-reported materials — not catalogue approval

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