Aca - Departamento de Física - Universidad Técnica Federico Santa ...

V Encuentro Sud Americano de Colisiones Inelásticas en la Materia
Manipulation of magnetic and electronic properties of Ga 1 - x Mn x As by ionbeam
irradiation
M. M. Sant’Anna 1 , T. G. Rappoport 1 , E. H. C. P. Sinnecker 1 , M. P. Pires 1 , G. M. Penello
1 , D. E. R. Souza 1 , S. L. A. Mello 1 , J. B. S. Mendes 1 , J. K. Furdyna 2 , and X. Liu 2
1 Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-909, RJ, Brazil
2 Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA
email address corresponding author: mms@if.ufrj.br
Spintronics relies on the simultaneous
use of both charge and spin degrees of freedom
of charge carriers. New materials have
been developed in recent years in order to
create a path towards the realization of spintronic
devices. The Ga 1-x Mn x As is one among
those materials. It has a crystalline structure
similar to Gallium Arsenide with a small
fraction of the Ga atoms replaced by Mn atoms.
The sites with Mn are diluted in the
original Ga 1-x Mn x As lattice.
The Ga 1-x Mn x As is a semiconductor
that also has magnetic characteristics. Its ferromagnetism,
however, is not a consequence
of direct Mn-Mn interactions. The relevant
Mn-Mn interaction is mediated by the holes
that are introduced by the Mn substitutional
to Ga (Mn Ga ). Thus, Mn Ga atoms in Ga 1-
xMn x As provide, at the same time, the holes
and the magnetic moments that are crucial for
the existence of magnetism in the material.
Intersticial Mn atoms, and other kinds of defects,
on the other hand, decrease the density
of carriers in the material. As a consequence,
magnetism is also decreased when Mn atoms
are displaced from Ga substitutional positions.
In practice, perfect crystalline Ga 1-
xMn x As is never grown and understanding the
role of defects in their magnetic and chargetransport
properties is fundamental in order
to control the behavior of this material (e.g.
[1]). Ion beams can displace the Mn atoms in
a controllable way. Thus, we have studied
Ga 1-x Mn x As with the controlled introduction
of defects by irradiating the samples with energetic
ion beam. Our recent study (Ref. [2])
focuses on the low-carrier-density regime,
starting with as-grown Ga 1-x Mn x As films and
decreasing even further the number of carriers,
through a sequence of irradiation doses.
We performed in situ room-temperature resistivity
measurements as a function of the ion
dose (Fig. 1).We have also studied the magnetization
as a function of temperature and of
the irradiation ion dose. We observe that both
magnetic and transport properties of the samples
can be experimentally manipulated by
controlling the ion-beam parameters.
Rs (Ω/sq)
10 5 x nom
=5%
Ga 1-x Mn x As
10 4
10 3
Li + (700 keV) + Ga 1-x
Mn x
As
Li + beam
p inicial
=2×10 14 cm -2
l = 4 mm
d = 100 nm
10 10 10 11 10 12 10 13 10 14 10 15
Dose (Li + /cm 2 )
Figure 1. Sheet Resistance as a function of the irradiation
dose measured in-situ for 700 keV Li + projectiles.
The sample is a 100 nm Ga 1-x Mn x As thin film
grown by MBE on a GaAs substrate.
References
[1] K. Sato et al., Rev. Mod Phys. 82, 1633
(2010).
[2] E. H. C. P. Sinnecker et al., Phys.
Rev. B. 81, 245203 (2010).
46 Valparaíso, Chile