Charge disorder induced magnetic order

In strongly correlated materials, clean non-magnetic samples, for example ruthenates[1-3], are sometimes found to develop long-range magnetic order via introduction of minute amount of non-magnetic disordered impurities. To explain such anti-intuitive behavior, we propose a scenario of inducing magnetic order via charge disorder in systems with coexisting local moment and itinerant degrees of freedom.  By disrupting the long-range quantum fluctuation originated from the itinerant carriers, the magnetic order preferred by the local moment can be re-established. We demonstrate this mechanism using a realistic spin-fermion model derived from the undoped FeSe as an example. We show that the magnetic order can indeed be recovered once the length scale of phase coherence of the itinerant carriers becomes shorter than that of the necessary quantum fluctuations as a result of enhanced disorder.  Our simple idea has a general applicability as it reflects the rich physics in quantum many-body systems through interplay between multiple components over different length scale.

[1] M. Braden et al., Phys. Rev. Lett.88, 197002 (2002).

[2] M. Minakata and Y. Maeno, Phys. Rev. B63, 180504 (2001).

[3] K. Ishida et al., Phys. Rev. B 67, 214412 (2003).