94. COMPOSITE STRUCTURES FOR BIT PATTERNED MEDIA (BPM)

Department: Electrical & Computer Engineering
Research Institute Affiliation: Center for Magnetic Recording Research (CMRR)
Faculty Advisor(s): Eric Fullerton

Primary Student
Name: Nasim Eibagi
Email: neibagi@ucsd.edu
Phone: 858-534-5853
Grad Year: 2015

Abstract
New functionality and performance advantages have been achieved in media by the formation of complex heterostructures. Examples include antiferromagnetically coupled ( AFC), exchange coupled composite ( ECC), and exchange spring media structures. Bit patterned media (BPM) provides unique opportunities for implementing these architectures because the transition noise is determined in the patterning process allowing considerable freedom in materials design. We will discuss recent experiments on [Co/Pd] multilayers and [Co/Pd]/Fe/[Co/Pd] heterostructures patterned in nano-dot arrays using self-assembled diblock copolymer as the etch mask. These structures were designed to reduce the coercive fields and switching field distributions (SFD) due to Fe soft coupling layer inside Co/Pd multilayers. These structures are also candidate material system for microwave assisted magnetic recording as the Fe layer resonant frequency is significantly lower than that of the Co/Pd layers. The SFD was analyzed for each sample at various temperatures and the ΔH (M, ΔM) method was used to extract the intrinsic SFD from total SFD [1]. Time dependent switching characteristics were analyzed at various magnetization points along the hysteresis loop to analyze the distribution of the energy barriers. We find strong variation in the measured energy barrier vary by an order of magnitude during reversal which can be quantitatively understood from the dipolar interactions of islands. We find the resonance frequency of the Fe interlayers can be tuned over a large frequency range by adjusting the Fe thickness and the coupling strength to the Co/Pd layers. We will compare the magnetic and resonant behavior of the film and patterned islands to micromagnetic calculations.

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