7.1 Composite Preparation by Codeposition of Metals
221
Fig. 7.1 Properties of granular Cu 75 Co 25 deposits. TEM image of the grain size structure in the
a as-received state and b after annealing at 400 °C, indicating the grain coarsening. c Variation of the
lattice parameters as a function of the annealing temperature (observation of the phase separation).
d Magnetization curves in the as-received and annealed states. Reprinted from [10]. Copyright
(2000), with permission from Elsevier
Annealing is a straightforward method to improve the properties of the granular
Cu–Co deposits. When annealing is carried out, various changes occur in the deposit
properties [8–13] for which a summary is shown in Fig. 7.1.
(i) Co atoms segregate from the metastable Cu–Co alloy. New lines appear in
the X-ray diffraction pattern that correspond to the pure Co phase. In parallel, the
diffraction line of the Cu-rich phase is shifted and returns to the position characteristic
of pure Cu. (ii) A grain coarsening takes place. (iii) The resistivity of the sample
decreases. This is because the weighted average of the resistivity of all phases and
that of the grain boundaries is less than the resistivity originating from the disorder
in the metastable Cu–Co crystals. (iv) The saturation magnetization increases upon
annealing. The reason of the increase in magnetization is that Co atoms embedded
in a non-magnetic matrix have no contribution to the total magnetization in the asreceived state. As a result of annealing, the segregation of Co grains enhances the
number of Co atoms that form grains with nonzero total magnetization, should they
belong to either SPM or FM particles. (v) The magnetoresistance ratio first increases,
then above a certain temperature decreases. The explanation of the initial increase of
the GMR is at least twofold, including the resistivity decrease of the matrix around the
magnetic particles as well as the increase in the spin-dependent electron scattering
intensity due to the increase in both the number and the volume of the magnetic
221
Fig. 7.1 Properties of granular Cu 75 Co 25 deposits. TEM image of the grain size structure in the
a as-received state and b after annealing at 400 °C, indicating the grain coarsening. c Variation of the
lattice parameters as a function of the annealing temperature (observation of the phase separation).
d Magnetization curves in the as-received and annealed states. Reprinted from [10]. Copyright
(2000), with permission from Elsevier
Annealing is a straightforward method to improve the properties of the granular
Cu–Co deposits. When annealing is carried out, various changes occur in the deposit
properties [8–13] for which a summary is shown in Fig. 7.1.
(i) Co atoms segregate from the metastable Cu–Co alloy. New lines appear in
the X-ray diffraction pattern that correspond to the pure Co phase. In parallel, the
diffraction line of the Cu-rich phase is shifted and returns to the position characteristic
of pure Cu. (ii) A grain coarsening takes place. (iii) The resistivity of the sample
decreases. This is because the weighted average of the resistivity of all phases and
that of the grain boundaries is less than the resistivity originating from the disorder
in the metastable Cu–Co crystals. (iv) The saturation magnetization increases upon
annealing. The reason of the increase in magnetization is that Co atoms embedded
in a non-magnetic matrix have no contribution to the total magnetization in the asreceived state. As a result of annealing, the segregation of Co grains enhances the
number of Co atoms that form grains with nonzero total magnetization, should they
belong to either SPM or FM particles. (v) The magnetoresistance ratio first increases,
then above a certain temperature decreases. The explanation of the initial increase of
the GMR is at least twofold, including the resistivity decrease of the matrix around the
magnetic particles as well as the increase in the spin-dependent electron scattering
intensity due to the increase in both the number and the volume of the magnetic