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ANNEALING EFFECT ON MAGNETIC
CHARACTERISTICS OF Pt/MnSb MULTILAYERED
FILMS
T. Kawanabe, M. Naoe
To cite this version:
T. Kawanabe, M. Naoe.
ANNEALING EFFECT ON MAGNETIC CHARACTERISTICS OF
JOURNAL DE PHYSIQUE
Colloque C8, Supplement au no 12, Tome 49, decembre 1988
ANNEALING EFFECT ON MAGNETIC CHARACTERISTICS OF Pt/MnSb MULTILAYERED FILMS
T. Kawanabe and M. Nme
Dept. of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Oh-okayama, Meguro-ku, Tokyo 152, Japan
Abstract. - Magnetic properties of Pt/MnSb multilayered films depend on annealing temperature and period. Distinct perpendicular anisotropy was found in the films composed of MnSb layers 50 A thick and Pt ones about 13
A
thick after annealing at 400 OC for 2.5 hours in vacuum. These films have perpendicular anisotropy constant K , of 4 x lo5 erg/cc.Introduction
Since PtMnSb Heusler alloy with a Clb type of structure is well known to have an extremely large Kerr rotation angle Bk [l, 21, its magnetic characteristics are interesting theoretically and its thin films are hopeful for magneto-optical recording media. Recently, several studies on the preparation of PtMnSb thin films with
large Ok by sputtering and vacuum evaporation have
been carried out [3, 41.
However, they have not yet been used for magneto- optical recording media because they do not have so large magnetization component perpendicular to film plane.
In this study, the preparation of Pt/MnSb multi- layered films with definitive perpendicular anisotropy composed of P t layers and MnSb ones by using Facing Targets Sputtering apparatus has been attempted and then, the annealing effects on magnetic characteristics of these films have been investigated.
Experimental procedure
Specimen films were deposited alternately on quartz glass substrates at temperature of 200 OC and at Ar gas pressure of 0.8 mTorr, using Facing Targets Sputter- ing (FTS) apparatus for depositing multilayered films, as shown in figure 1. It can deposit the very smooth thin layers on the plasma-free substrates with high mo- bility of adatoms and without undesirable damage of good crystal orientation due to bombardment of high energy particles [5]. P t layers with various thickness and MnSb ones 50 b; thick were alternately deposited
until total thickness of multilayered film became up t o about 2 000 b; and the ratio in thickness of P t layer
Rpt=Spt
/
( S P ~ + ~ M ~ S ~ ) were varied in the range of 6-35 %,
where 6pt and 6~,,sb were thickness of P t layer and that of MnSb one, respectively. Two rolled Pt plates and two MnaoSbso sintered ones with pu- rity of 99.9 % were used as two pairs of facing targets. Annealing of as-deposited films were performed at 300 and 400 OC for 5 to 150 rnin. in vacuum at residualpressure below 1 x Torr. Magnetic properties were
Fig. 1. - Facing Targets Sputtering apparatus.
determined by using vibrating sample magnetometer (VSM) and torque magnetometer.
Results a n d discussion
Magnetic properties of alternately deposited
Pt/MnSb films depended on Pt ratio in thickness of P t layer Rpt, as shown in figure 2. Saturation magnetiza-
1
n anneal 400.0 150 mln1
Fig. 2. - Dependence of saturation magnetization M, and perpendicular coercivity HcI on Pt thickness ratio RPt.
C8 - 1784 JOURNAL DE PHYSIQUE
tion M, of as-deposited and annealed films decreased
with increase of R p t Ms of annealed films were larger than that of as-deposited ones for R p t up to 26 %
.
Perpendicular coercivity H,J- of as-deposited films de-
pended on Rpt and took maximum at R p t around
13 %. Since an increase of Hc may be attributed to the
magnetic jumps observed at magnetic field of about
200 Oe in the hysteresis loop on the direction normal
to the film plane. After annealing, H,L at R p t of 6
and 13 % decreased, while that at R p t of 20, 26 and
35 % increased. Since annealed films at 26 % R p t has coercivity as high as about 300 Oe, the dependences of magnetic properties on annealing temperature and period were studied in detail.
Figure 3 shows dependence of perpendicular coer- civity H c l on annealing temperature and period. H c l
of films annealed a t 300 O C increased with increase
of annealing period up to 20 min rapidly and above
20 min monotonically. On the other hand, HcL of
films annealed at 400 OC increased drastically up to
5 min and decreased monotonically above 5 min with
increase of annealing period. These phenomena seem t o be attributed to the release of internal stress in the
as-deposited films by annealing.
1 I
50 1M) 150
ANNEALING PERIOD ( m i n )
Fig. 3. - Effects of annealing temperature and period on perpendicular coercivity HcI.
Figure 4 shows perpendicular anisotropy constant
Ku in the films deposited at R p t of 13 to 35 % and annealed at 400 O C for 2.5 hours. Ku took maximum
at R p t of about 20 % and Clb type phase of PtMnSb heusler alloy were formed in this film. Such a large
Fig. 4. - Dependence of perpendicular anisotropy constant
Ku on ratio in thickness of Pt layer RPt.
perpendicular anisotropy seems to be attributed to the enhanced anisotropy effects at many interfaces in mul- tilayered films, but the mechanism on these effects has not yet been made clear.
Conclusion
Preparation of Pt/MnSb multilayered films with dis- tinct perpendicular magnetic anisotropy have been at- tempted depositing Pt layers and MnSb ones alter-
nately by using plasm+free FTS apparatus. Magnetic
properties of these films depended strongly on anneal- ing temperature and period. The multilayered films
composed of MnSb layers 50 thick and Pt ones about
13 thick had perpendicular anisotropy constant
Ku
as large as 4 x lo5 erg/cc after annealing at 400 OC for
2.5 hours in vacuum.
[I] Van Engen, P. G., Buschow, K. H. J., Jongebreur, R. and Erman, M., A p p l . Phys. Lett. 42 (1983) 202.
[2] De Groot, R. A., Mueller, F. M., van Engen, P. G. and Buschow, K. H. J., Phys. Rev. Lett. 50 (1983) 2024.
[3] Ohyarna, R., Abe, J. and Matsubara, J. Magn.
Soc. Jpn 9 (1985) 145.
[4] Inukai,
T.,
Matsuoka, M. and Ono, K., Appj.Phys. Lett. 49 (1986) 52.
[5] Naoe, M., Yamanaka, S. and Hoshi, Y., IEEE
