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The metal-insulator transition in Fe(1.01-x)Cu(x)Se
A J Williams1, T M McQueen, V Ksenofontov
1Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
Adding copper to iron selenide (Fe(1.01)Se) suppresses superconductivity and induces a metal-insulator transition. Doping with copper also introduces local magnetic moments, leading to a spin-glass transition at low temperatures.
Area of Science:
- Condensed matter physics
- Materials science
- Solid-state chemistry
Background:
- Iron selenide (Fe(1.01)Se) is a layered compound known for superconductivity at 8 K.
- It serves as a parent compound for superconducting arsenides.
- Previous studies indicated Fe(1.01)Se is non-magnetic.
Purpose of the Study:
- Investigate the effects of copper substitution on the properties of Fe(1.01)Se.
- Determine the solubility limit of copper in Fe(1.01)Se.
- Characterize the magnetic and electronic transitions induced by copper doping.
Main Methods:
- Solid-state synthesis and substitution of copper at iron sites in Fe(1.01)Se.
- Structural analysis to determine solubility limits and phase transitions.
- Measurements of electrical resistivity and magnetic susceptibility to probe electronic and magnetic properties.
Main Results:
- Copper substitution in Fe(1.01)Se is possible up to 20-30% solubility.
- A first-order structural transition to the CuFeSe(2) type occurs beyond the solubility limit.
- Superconductivity is suppressed by as little as 1.5% copper doping.
- A metal-insulator transition is observed at 4% copper doping.
- Local magnetic moments are introduced, maximizing near 12% doping.
- A spin-glass transition occurs near 15 K at approximately 12% doping.
Conclusions:
- Copper substitution significantly alters the electronic and magnetic properties of Fe(1.01)Se.
- The introduction of copper drives phase transitions, including structural, metal-insulator, and spin-glass transitions.
- This study reveals a complex interplay between structure, magnetism, and superconductivity in copper-doped iron selenides.
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