MAGNETIC CONFIGURATION IN ANTIFERROMAGNETICALLY COUPLED [Co/Pd]15/TbFeCo WITH OUT-OF-PLANE ANISOTROPY
We have used Polarized Neutron Reflectometry (PNR) to investigate the magnetic properties of an exchange-coupled bilayer system with out-of-plane magnetization. These systems show potential for increasing storage densities in magnetic recording media by manipulating the out-of-plane magnetization instead of in-plane. To probe the nature of the interfacial coupling, we have studied the field-dependent magnetic structure of bilayers using a novel geometry for PNR, which is sensitive to the depth-dependent vector magnetizations of individual FM layers on sub-nanometer length scales. Magnetization measurements suggest the formation of an in-plane domain wall. The magnetic configuration inside such systems results from the competition between the magnetic field, short-range exchange coupling, and long-range dipolar interactions. This study involved [Co(0.5 nm)/Pd(X)]15/TbFeCo(25 nm) (X=3.5, 5, 7 nm) structures. Both the [Co/Pd] and TbFeCo exhibit strong out-of-plane anisotropy and are exchange coupled antiferromagnetically due to the TbFeCo alloy concentration which acts a stabilizing pinning layer. The magnitude of exchange coupling between the Co layers may be modified by changing the Pd thickness. PNR measurements, which are sensitive to the in-plane component of the magnetization only, confirm the formation of an in-plane domain wall that varies with the exchange stiffness inside the Co/Pd and with the field. The extent of the in-plane domain wall decreases with increasing applied field for the films with Pd thicknesses of 7 and 5 nm whereas the behavior of the thinnest film (Pd = 3.5nm) suggests the Co/Pd bilayers show no evidence of a domain wall.
In collaboration with J.A. Borchers, T. Hauet, S. Mangin, and E.E. Fullerton
Name: Shannon Watson
Mentor: Julie Borchers
Bldg 235, Rm E129
Sigma Xi: No