Micromagnetics Simulation of Asymmetricpseudo-Spin Valve Dots
- PDF / 681,988 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 57 Downloads / 181 Views
Micromagnetics Simulation of Asymmetric Pseudo-Spin Valve Dots N. Dao,1 C. A. Ross,2 F. J. Castaño,2 M. J. Donahue,3 and S. L. Whittenburg1 1 Department of Chemistry/AMRI, University of New Orleans, New Orleans, LA 70148, U.S.A. 2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A. 3 National Institute of Standards and Technology, Gaithersburg, MD 20899, U.S.A.
ABSTRACT We present simulation results for Ni79Fe21 (5 nm)/Cu (3 nm)/Co (4nm) pseudo-spin valves. These simulations have been conducted on several different aspect ratios of rectangular dots. Distinct switches of the two magnetic layers were observed. At smaller aspect ratios, magnetization reversal proceeds through a leaf state in the soft layer and a flower state in the hard layer. For larger aspect ratios, reversal proceeds by nucleation and annihilation of domain walls. Our simulations show a reasonable agreement with the experimental results. Differences between the experimental and simulation results are discussed.
INTRODUCTION Research in Magnetoresistive Random Access Memory (MRAM) has been very active since MRAM provides a competitive memory compared to Dynamic Random Access Memory (DRAM) and Flash technology [1]. The promising structures for future MRAM are magnetic tunnel junctions and pseudo-spin valves [2-4]. There have been recent reports of fabrication of pseudo-spin valves with sub-100 nm dimensions [5-7]. By using micromagnetics simulation, the magnetic states occurring during the switching process can be determined, which will aid in designing a magnetic device. In this study, we apply micromagnetics to examine the magnetization reversal process in rectangular pseudo-spin valve elements. The soft layer is permalloy and the hard layer is cobalt. The switching mechanism of these magnetic layers will be addressed.
PROCEDURE Our calculations were performed on Ni79Fe21 (5 nm, bottom layer)/Cu (3 nm)/Co (4 nm, top layer) pseudo-spin valves. The experimental pseudo-spin valve of Ni79Fe21 (6 nm)/Cu (3 nm)/ Co (4 nm)/Cu (4 nm) was deposited by DC sputtering and patterned by interference lithography into rectangular dot arrays [5, 7] with widths of 70-90 nm and aspect ratios of 1.5-10. The experimental thicknesses of 6, 3, and 4 nm are nominal and the “real” thickness is probably different. Slightly better agreement with the experimental loops was obtained by using a 5 nm permalloy layer. The spacing between the dots in an array is three times the width and two times the length of the dot. The magnetostatic interaction between these dots is negligible. In this work, we simulated only a single dot. The simulated hysteresis loops were obtained from dots with a range of aspect ratios from 1.8 to 7.9. The experimental loops were obtained using MicroMagTM 2900 alternating gradient magnetometer.
W5.7.1 Downloaded from https:/www.cambridge.org/core. Cornell University Library, on 15 Jun 2017 at 18:36:25, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/t
Data Loading...
