Positive magnetoresistance peaked at ferromagnetic transition in Mn-doped quantum wells GaAs/AlGaAs
N. V. Agrinskaya+, V. A. Berezovets+*, V. I. Kozub+
+Ioffe Physico-Technical Institute of the RAS, 194021 S.Petersburg, Russia
*International Laboratory of High Magnetic Fields and Low Temperatures, 53421 Wroclaw, Poland
Abstract
A large positive magnetoresistance peaked at the Curie temperature
was observed in quantum well structures GaAs/AlGaAs doped by Mn.
We suggest a new mechanism of magnetoresistance within low Tc ferromagnets
resulting from a pronounced dependence of spin polarization at the vicinity
of Tc on the external magnetic field. As a result, any contribution to
resistance dependent on the Zeeman splitting of the spin subbands is
amplified with respect to the direct effect of the external field. In our
case we believe that the corresponding contribution is related to the upper
Hubbard band. We propose that the mechanism considered here can be exploited
as the mark of ferromagnetic transition.