Magnetic and thermodynamic properties of cobalt doped iron pyrite: Griffiths Phase in a magnetic semiconductor

Abstract

Doping of the band insulator FeS${}_2$ with Co on the Fe site introduces a small density of itinerant carriers and magnetic moments. The lattice constant, AC and DC magnetic susceptibility, magnetization, and specific heat have been measured over the $0\le x\le 0.085$ range of Co concentration. The variation of the AC susceptibility with hydrostatic pressure has also been measured in a small number of our samples. All of these quantities show systematic variation with $x$ including a paramagnetic to disordered ferromagnetic transition at $x=0.007\pm 0.002$. A detailed analysis of the changes with temperature and magnetic field reveal small power law dependencies at low temperatures for samples near the critical concentration for magnetism, and just above the Curie temperature at higher $x$. In addition, the magnetic susceptibility and specific heat are non-analytic around H=0 displaying an extraordinarily sharp field dependence in this same temperature range. We interpret this behavior as due to the formation of Griffiths phases that result from the quenched disorder inherent in a doped semiconductor.

22 pages including 27 figures

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Cited by in corpus (7)

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• Electrical and magnetic properties of the complete solid solution series between SrRuO3 and LaRhO3: Filling t2g versus tilting
• Contrasting Ferromagnetism in Pyrite FeS${}_2$ Induced by Chemical Doping versus Electrostatic Gating
• Quantum Griffiths singularities in ferromagnetic metals
• Strong-disorder magnetic quantum phase transitions: Status and new developments
• Transport properties in antiferromagnetic quantum Griffiths phases
• Monte Carlo simulations of the disordered three-color quantum Ashkin-Teller chain