CORRELATION BETWEEN ATOMIC
ORDERING AND MAGNETIC PROPERTIES
IN
FePtCu THIN FILMS
S. Laureti a, C. Brombacherb, D. Makarovb, M. Albrechtb, D.
Peddis a, G. Varvaro a, and F. D’Acapitoc
ISM-CNR, Area della Ricerca RM1, Via Salaria Km 29,300, P.B. 10-00015, Monterotondo Scalo, Roma, Italy
Institute of Physics, Chemnitz University of Technology, Chemnitz, Germany
c CNR-IOM-OGG c/o ESRF, LISA (ex GILDA) Grenoble, France
a
b
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SIF 2015- Roma, 21 - 25 September 2015
The message
EXAFS to understand the MAGNETIC PROPERTIES
The system
3d-5d based alloys: FePt, CoPt, CoPd…
c
Easy axis
a
b
Ordered fct (L10)
Disordered fcc (A10)
low anisotropy
magnetically soft
in-plane
M
high magnetocrystalline anisotropy
magnetically hard
out of plane
•Artificial layering
•Strain/pressure
M
•addition of a third element (Ag, Cu…)
•………………
H
H
FePtCu
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SIF 2015- Roma, 21 - 25 September 2015
2
Magnetic behaviour
300 K hysteresis loop (SQUID)
8
7
6
-3
Keff (10 ergcm )
6
5
4
3
2
1
0
-1
0
5
10
15
20
25
Cu (at %)
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SIF 2015- Roma, 21 - 25 September 2015
3
Exafs results
Pt –LIII EDGE: DATA
Parallel to the film
WHY?
high sensitivity
element selectivity
HOW?
Exp:
fluorescence
polarized beam
mode,
Fit: linear combination between
DIRECT (Pt on Pt sites) and
INVERSE (Pt on Fe sites)
structure
Perpendicular to the film
WHAT?
-Pt-LIII edge
-Cu-K edge
-Pt-Pt and Pt-Fe distances,
the shift of the energy origin
Debye-Waller Factor
X-chemical order
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S. Laureti, et al., J. Appl. Cryst. 47 (2014) 1722
SIF 2015- Roma, 21 - 25 September 2015
4
Exafs results
Cu content
Monotonic
reduction of c/a
Non-monotonic
behavior of X
Cu at Fe sites
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SIF 2015- Roma, 21 - 25 September 2015
5
CONCLUSIONS
S. Laureti, et al., J. Appl. Cryst. 47 (2014) 1722
10
9
7
6
Magnetic Anisotropy
5
6
3
Keff [10 erg/cm ]
8
4
From SQUID measurements
3
2
1
0
0
5
10
15
20
25
Cu content - at. %
tetragonal distortion
EXAFS
0.9
0.95
0.8
0.94
c/a
X-chemical order
Chemical order
0.7
0.93
0.92
0.6
0.91
0.5
0
0
5
10
15
20
25
5
10
15
20
25
Cu content - at. %
Cu content - at. %
[email protected]
SIF 2015- Roma, 21 - 25 September 2015
6
[email protected]
SIF 2015- Roma, 21 - 25 September 2015
7