M. Chladek et al., STRUCTURAL AND MAGNETIC ANALYSIS OF NI81FE19 AG MULTILAYERS WITH ULTRATHIN NI81FE19 SUBLAYERS/, Journal of physics. Condensed matter, 9(22), 1997, pp. 4557-4574
The magnetic and structural properties of Ni81Fe19/Ag multilayer films
with very thin sublayers of the magnetic Ni81Fe19 component, ranging
from 5 Angstrom to 10 Angstrom, were studied. A transition from a near
ly pure superparamagnetic behaviour (t(NiFe) = 5 Angstrom) to a nearly
ferromagnetic behaviour (t(NiFe) = 10 Angstrom) was observed, with a
transition at the Ni81Fe19 layer thickness of about 7 Angstrom. The ob
served differences in magnetic properties are thought to be mainly con
nected with the size of the NiFe particles in the magnetic sublayers,
which can be controlled by their thickness. The structure of the magne
tic sublayers becomes more disturbed with decreasing thickness, as can
be judged from the in-plane correlation length, roughness, and strain
, and the numbers of precipitated crystallites of the two components.
The influences of various annealing processes were examined, and the s
tructural changes were followed in situ by high-angle x-ray diffractio
n (XRD). The temperature treatment increased the magnetoresistance rat
io. We observed a gradual growth of the content of silver and NiFe pre
cipitates with increasing annealing, temperature. The structure of the
original multilayers gradually deteriorates with increasing temperatu
re, and the whole complex consists of a mixture of residual multilayer
blocks and precipitates. The observed structural characteristics of t
he multilayers under study have been found essential to the understand
ing of their magnetic properties.