1202.3207 (V. Tripathi et al.)

Resistance noise in a two-dimensional hole gas affected by magnetic
impurities    [PDF]

V. Tripathi, Kusum Dhochak, B. A. Aronzon, Bertrand Raquet, V. V. Tugushev, K. I. Kugel

We study theoretically and experimentally the frequency and temperature
dependence of resistivity noise in semiconductor heterostructures delta-doped
by Mn. The resistivity noise is observed to be non-monotonous as a function of
frequency. As a function of temperature, the noise increases by two orders of
magnitude for a resistivity increase of about 50%. We study two possible
sources of resistivity noise -- dynamic spin fluctuations and charge
fluctuations, and find that dynamic spin fluctuations are more relevant for the
observed noise data. The frequency and temperature dependence of resistivity
noise provide important information on the nature of the magnetic interactions.
In particular, we show how noise measurements can help resolve a long standing
debate on whether the Mn-doped GaAs is an p-d Zener/RKKY or double exchange
ferromagnet. Our analysis includes the effect of different kinds of disorder
such as spin-glass type of interactions and a site-dilution type of disorder.
We find that the resistivity noise in these structures is well described by a
disordered RKKY ferromagnet model dynamics with a conserved order parameter.

View original: http://arxiv.org/abs/1202.3207