HAL Id: jpa-00229071
https://hal.archives-ouvertes.fr/jpa-00229071
Submitted on 1 Jan 1988
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of
sci-entific research documents, whether they are
pub-lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
MAGNETIC PROPERTIES OF Ni/Si MULTILAYERS
M. Pérez-Frías, B. Martínez, M. Moreu, J. Tejada, J. Vicent
To cite this version:
M. Pérez-Frías, B. Martínez, M. Moreu, J. Tejada, J. Vicent.
MAGNETIC PROPERTIES
JOURNAL DE PHYSIQUE
Colloque C8, Supplement au no 12, Tome 49, decembre 1988
MAGNETIC PROPERTIES OF Ni/Si MULTILAYERS
M. T. Perez-Mas (I), B. Martinez ('), M. A. Moreu (3), J. Tejada (3) and J. L. Vicent ( I )
(I) Depto. Fisica de Materiales, Facultad Ciencias Fisicas, Universidad Complutense, 28040 Madrid, Spain
(') Institut de Ciencia de Materials C.S.I.C., 08028 Barcelona, Spain
(3) Facultad de Fisica, Universidad de Barcelona, Diagonal 647.08028 Barcelona, Spain
Abstract. - Multilayers of Ni/Si have been fabricated by D.C. triode sputtering. X-ray diffraction patterns were made in the reflection geometry. The diffraction patterns show peaks at small angles. High angle diffraction does not show any texture in Ni and Si layers. The dependence of magnetization with the temperature and the applied magnetic field is studied.
Multilayered samples are the ideal tool to study the interplay between two materials [l] with, for ex- ample, the possibility t o modify the long range order properties of one of them.
In this report we present data above the fabrication, characterization by X-rays and magnetic measure- ments in magnetic/nonmagnetic multilayers of Ni/Si.
Multilayers of Ni/Si were grown by D.C. triode sput- tering in the usual way [2] alternately depositing Ni and Si layers using the appropriate two independent cathodes in each case. The films were deposited onto unheated Corning glass substrates. The deposition rate was measured with a quartz crystal oscillator, be- ing about 0.6 As-' for Ni and 1.1
&-'
for Si. The base pressure was 5 x Torr and the Ar pres- sure 0.5 mTorr. Standard X-ray diffraction were ob- tained in the reflection geometry with a Siemens D-500 diffractometer using CuX, radiation and 6'/
2 6' andw (rocking) scans were done.
The composition modulation wavelength D is known monitoring the deposition rate and the time which the substrate spent in front of each cathode. Besides the D value could be extracted, for short wavelength, from the X-ray data [2]. The bilayer D values obtained by both method were consistent to within 10 %
.
The diffraction pattern of a multilayer shows peaks at small angle coming from the periodic composition modula- tion. Figure la shows the small angle data of a sample of Ni/Si with D = 30A.
In the inset of figure l a , the rocking curve shows a very small undulations of the layers. Figure l b shows the high angle data in Ni/Si. The amorphous character of the sample is clear.Magnetic measurements were done with a SHE- SQUID magnetometer. The only problem in the mag- netization data was the Corning glass substrate and the small amount of Ni in our multilayers. The rough data were corrected from substrate contribution by measuring several dummy substrates. The total thick- ness of the samples was 2 000
A
and the bilayer thick- nesses D were between 30A
and 200A.
The maximum applied magnetic field was 5 T , and the lowest temper- ature was 1.8 K.Fig. 1. - (a) Small-angle 8/28 X-ray diffraction pattern for a Ni/Si multilayer with D = 30 A. Rocking curve of the first order peak in the inset. (b) High angle 8/28 X-ray scan for Ni/Si multilayer with D = 30
A.
Figure 2 shows the magnetization behavior versus
applied magnetic field. Figure l a shows a typical hys- teresis loop, figure 2b shows the possible role of super- paramagnetism clusters in the Ni/Si interface regions, magnetization curves measured at different tempera- tures do not superimpose when M is plotted as a func- tion of H
/
T. Both behavior could indicate that the ferromagnetism dominates in this Ni/Si system.Figure 3 shows the temperature dependence of the saturation magnetization. We have t o take into ac-
count that extrapolating to zero M, is not the way to
C8
-
1788 JOURNAL DE PHYSIQUEalso observed a more moderate enhancement in B in Fe/Ag. The possible role of the interfaces in the high values of 3 and C and the negative value of C is un-
clear at present.
get the Curie temperature T,, Arrot plots have t o be done to get reliable values of
T,.
We get a good agree- ment between the experimental M, (T) data and a 3-Dspin-waves behaviour (see Tab. I). The experimental data were fitted following the method of [3]. We can observe that the values are higher than in pure Ni and
C is negative. this means that the stiffness constant
is extraordinary low. This very large values of B and
C are similar t o the multilayer system (Fe75Si25)
/
Si reported by Martinez et al. 181. Walker et al. [9] have[I] Chun, C . S. L., Zheng, G. G., Vicent, J. L.,
S~huller, I. K., Phys. Rev. B 29 (1984) 4915. [2] Skhuller, I. K., Phys. Rev. Lett. 44 (1980) 1577.
[3] Puzniak, R., Dmowski, W., J. Phys. F. 17 (1987) 1437.
[4] Martinez, B., Moreu, M. A., Labarta, A.,
Obradors, X., Tejada, J., J . A p p l . Phys. 63 (1988) 3206.
[5] Walker, J. C., Droste, R., Stern, G., Tyson, J., J. A p p l . Phys. 55 (1984) 2500.
,
.v I • v D = ~ O A .v * v A D = 4 0 A v D = ~ O A.
v A ..
v D = 2 0 0 A v . ~ v v ' t V V . A V V * A.
A 1.0. 0.mQ
$ 0 5 C 7 b/.
- 1 - wa B 0.25 0 lb 20 3 b TCK)Fig. 3.
-
Normalized saturation magnetization versus tem-perature in Ni/Si multilayers.
Table I. 01
.
sE
d B 0 I 5 L 1 0 H I T ( ~ o e I K 1Fig. 2. - (a) Hysteresis loops with applied field perpendic- ular t o the film plane ( 6 ) decreasing field, (A) increasing field, in Ni/Si multilayer (D = 60 A)
