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Doped magnetic moments in a disordered electron system: insulator-metal transition, spin glass and `cmr'

Sanjeev Kumar·Pinaki Majumdar
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Abstract

Recent experiments on the amorphous magnetic semiconductor Gd_x Si_{1-x}, Phys. Rev. Lett. 77, 4652 (1996), ibid 83, 2266 (1999), ibid 84, 5411 (2000), ibid 85, 848 (2000), have revealed an insulator-metal transition (i-m-t), as a function of doping and magnetic field, a spin glass state at low temperature, and colossal magnetoresistance close to the i-m-t. There are also signatures of strong electron-electron interaction close to the i-m-t. Motivated by these results we examine the role of doped magnetic moments in a strongly disordered electron system. In this paper we study a model of electrons coupled to structural disorder and (classical) magnetic moments, through an essentially exact combination of spin Monte Carlo and fermion exact diagonalisation. Our preliminary results, ignoring electron-electron interactions, highlights the interplay of structural and magnetic `disorder' which is primarily responsible for the observed features in magnetism and transport.

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Sanjeev Kumar, Pinaki Majumdar. 2001-01-20. Doped magnetic moments in a disordered electron system: insulator-metal transition, spin glass and `cmr'. https://doi.org/10.1142/s0217979201006562

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