The Effects of Substrate Preheating and Post-Deposition Annealing on CrMn/CoCrPt/CrMn/NiAI Films
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The compositions of the CoCrPt films determined by energy dispersive x-ray spectroscopy (EDX) were 78 at% Co, 6 at% Cr, and 16 at% Pt. The Mn concentration of the CrMn alloy films deposited in this study was 22 at%. The in-plane magnetic properties of the samples were measured using a vibrating-sample magnetometer (VSM) and an alternating-gradient magnetometer (AGM) with a maximum applied field of 10 kOe. Film textures were examined by 0-20 scan x-ray diffractometry with CuKoa radiation. RESULTS AND DISCUSSION The in-plane coercivities, Ms, AM/Mr peak values, and S* for CoCrPt/CrMn/NiAI films are plotted against the CrMn intermediate layer thickness in Fig. 1 (a)-(d), respectively. Data for samples deposited with substrate preheating to 260 'C and without preheating are shown. Selected x-ray 0-20 scans of the above films are shown in Figs. 2 and 3 for comparison.
800
4000
3000
600 -k
2000
400
1000
200 * no preheating Eo preheating: 260'C
*
no preheating 5 preheating: 260°C 0
0 0 200 400 600 800 CnMn Intem-ediate Layer Thickness (A)
1000
Q 200 400 600 800 CtMn Intemediate Layer Thickness (A)
1000
(b)
(a) I 0.8
0.81
0.6
0.6
0.4
0.4
0.2
0.2
no preheating 0 preheating: 260'C 0
03 0 200 400 600 800 CnMn Intem-ediate Layer Thickness (A)
0
1000
0
I
* no preheating 5 preheating: 260'C 0
200 1000 400 600 800 CdMlnIntemediate Layer Thickness (A)
(d)
(c)
Fig. 1 In-plane magnetic properties (a) coercivity, (b) Ms, (c) AM/Mr peak, and (d) S* as functions of CrMn thickness for CoCrPt(300,A)/CrMn(x)/NiAl(1000A) films deposited with or without substrate preheating.
218
orCrl.. CoCrPt NiMA (0010) (110)
600
600
~ ~CrK~n:l OOA Hc:291 0 0"ý
SCrMn:1 OOOA Hc:3070 Oe 400
-IL
,
C: En F_~
200A
NiAlor CrK~n
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0
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20
, 0 30
. 40
oA 50
60
2480 Oe 70
K• /L 0 .. . . 40 30
80
20
9oA 50
60
2260 Oe 70
80
20
Fig. 3 X-ray diffraction spectra of 300 A CoCrPt films on various thickness of CrMn intermediate layers on top of 1000 A NiAI underlayers. Substrate preheating: 260 'C.
Fig. 2 X-ray diffraction spectra of 300 A CoCrPt films on various thickness of CrMn intermediate layers on top of 1000 A NiAI underlayers. No substrate preheating.
Without substrate heating, adding a CrMn intermediate layer as thin as 25 A between the CoCrPt magnetic layer and the NiAl underlayer increased the coercivity by 900 Oe and improved the CoCrPt (1010) texture. No further improvement in the coercivity or the Co-alloy texture was obtained by increasing the CrMn thickness. This is similar to the effect reported for Cr and CoCrTa intermediate layers [8,9]. Contrary to the results reported for CrMn underlayers [7], we have found that for the combined CrMn/NiAl underlayers, applying substrate heating degraded the CoCrPt texture and the coercivity decreased. The Ms values for samples prepared with no preheating are essentially independent of CrMn thickness and are around 560 emu/cc. When substrate preheating was applied, the Ms of the films with
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