비정질 강자성체 CoSiB/Pd 다층박막의 두께에 따른 수직자기이방성 변화

다국어 초록 (Multilingual Abstract)

Perpendicular magnetic anisotropy (PMA) is the phenomenon of magnetic thin film which is preferentially magnetized in a direction perpendicular to the film’s plane. Amorphous multilayer with PMA has been studied as the good candidate to realization of high density STT-MRAM (Spin Transfer Torque-Magnetic Random Access Memory). The current issue of high density STT-MRAM is a decrease in the switching current of the device and an application of amorphous materials which are most suitable devices. The amorphous ferromagnetic material has low saturated magnetization, low coercivity and high thermal stability. In this study, we presented amorphous ferromagnetic multilayer that consists of an amorphous alloy CoSiB and a nonmagnetic material Pd. We investigated the change of PMA of the [CoSiB t<SUB>CoSiB</SUB>/Pd 1.3 nm]? multilayer (t<SUB>CoSiB</SUB> = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 nm, and t<SUB>Pd</SUB>= 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 nm) and [CoSiB 0.3 nm/Pd 1.3 nm]n multilayer (n = 3, 5, 7, 9, 11, 13). This multilayer is measured by VSM (Vibrating Sample Magnetometer) and analyzed magnetic properties like a coercivity (Hc) and a magnetization (Ms). The coercivity in the [CoSiB t<SUB>CoSiB</SUB> nm/Pd 1.3 nm]? multi-layers increased with increasing t<SUB>CoSiB</SUB> to reach a maximum at t<SUB>CoSiB</SUB> = 0.3 nm and then decreased for t<SUB>CoSiB</SUB>> 0.3 nm. The lowest saturated magnetization of 0.26 emu/cm³ was obtained in the [CoSiB 0.3 nm/Pd 1.3 nm]₃ multilayer whereas the highest coercivity of 0.26 kOe was obtained in the [CoSiB 0.3 nm/Pd 1.3 nm]? mutilayer. Additional Pd layers did not contribute to the perpendicular magnetic anisotropy. The single domain structure evolved in to a striped multi-domain structure as the bilayer repetition number n was increased above 7 after which (n > 7) the hysteresis loops had a bow-tie shapes.

참고문헌 (Reference)

1 F. J. A. den Broeder, 60 : 2769-, 1988

2 G. A. Bereto, 134 : 173-, 1994

3 S.-I. Iwasaki, 11 : 1173-, 1975

4 J. F. Weaver, 50 : 107-, 2003

5 N. Nishiura, 91 : 5246-, 2002

6 G. H. O. Daalderop, 68 : 682-, 1992

7 J. Y. Hwang, 310 : 1943-, 2007

8 J. Y. Hwang, 2009

9 J.-H. Park, 103 : 07A917-, 2008

10 G. H. O. Daalderop, 50 : 9989-, 1994

11 J. Carrey, 83 : 5259-, 2003

12 V. W. Gue, 45 : 2686-, 2009

13 B. Window, A4 : 996-, 1986

14 D. Weller, 89 : 7525-, 2001

15 정솔, "Perpendicular Magnetic Anisotropy of Amorphous Ferromagnetic CoSiB/[Pt,Au] Multilayer" 한국물리학회 60 (60): 450-453, 2012