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Start of funding 01.01.2015
Curie-temperature modulated composite media for thermally assisted magnetic recording
Prof. Dr. Manfred Albrecht
University of Augsburg
Lehrstuhl für Experimentalphysik IV
Dr. Stefan Maat
HGST, Inc.
HSGT, San Jose
In order to provide enough long term thermal stability of a magnetic storage unit (bits), one needs to use material with high magnetic anisotropy such as L10 ordered FePt alloys. However, these materials require large magnetic fields to switch their magnetization. This issue can be overcome by raising the temperature during the writing process close to its Curie temperature. However, elevated temperatures also lower the magnetization which ubstantially increase thermally induced recording errors. In this regard, a composite media structure, consisting of two exchange-coupled layers with different Curie temperatures, has been proposed to overcome the above limitations. The goal of this proposal is to develop a new exchange-coupled double layer prototype system based on L10 ordered FePtCu combined with [Co/Ni] multilayers and to demonstrate its capability as recording material.
Final report:
During the joint research project with HGST (a Western Digital Company) an exchange coupled composite media consisting of L10-ordered FePtCu combined with a ferrimagnetic amorphous alloy was prepared and analyzed. 5 nm thick (Fe100-xCux)52Pt48 (x = 0,15, 20 at.%) were deposited on thermally oxidized Si-substrates exhibiting perpendicular magnetic anisotropy after rapid thermal annealing. Different magnetic properties and especially a decreasing Curie temperature was obtained with increasing Cu content. Additionally, 20 nm thick amorphous Tb-dominated Tb26CoyFe100-x-y (x = 0, 44, 100 at.%) films with perpendicular magnetic anisotropy were deposited on top of the ferromagnetic layer. Temperature dependent SQUID – VSM magnetometry measurements were performed to analyze the switching and coupling behavior, revealing a strong exchange bias shift of the ferri- or ferromagnetic layer, depending on the magnetic coupling condition at the interface.
Further joint studies on this research topic are currently planned.