Asymmetric magnetoresistance in an exchange bias Co/CoO bilayer.
Magnetoresistance (MR) measurements are carried out on a Co(8 nm)/CoO(3.5 nm) bilayer in the exchange bias (EB) state prepared by molecular beam epitaxy. With the applied magnetic field parallel to the current, the EB MR curves show an asymmetric behavior about the minimum, in contrast to the symmetric one for non-EB systems. We generalize a well-known analytical expression used for the field dependence of the MR of paramagnets. Our generalization incorporates coercivity and EB in a new phenomenological MR expression. Excellent fits of the latter to the experimental MR data are achieved, showing the way to use MR techniques for the quantitative characterization of EB systems. Furthermore, the temperature dependence of the EB field obtained from MR loops can be described with a power law, which yields a value of 96.6 K for the EB blocking temperature, which is significantly below the Néel temperature of 293 K for bulk CoO.
Department of Physics and Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0111, USA. sarbeswar@gmail.com
Sarbeswar
S
Sahoo
Srinivas
S
Polisetty
Yi
Y
Wang
Tathagata
T
Mukherjee
Xi
X
He
Sitaram S
SS
Jaswal
Christian
C
Binek
D003035:Cobalt / Q000737:chemistry*; D060526:Magnetic Fields; D010087:Oxides / Q000737:chemistry*; D013696:Temperature
D010087:Oxides; D003035:Cobalt; C060728:cobalt oxide