Influence of Intermediate Ag Layer Thickness on Phase Transformations in FePt/Ag/FePt Thin Film Compositions
Keywords:Magnetic recording, Film compositions, FePt, Coercivity
Background. Film compositions with chemically ordered and magnetically hard L10-FePt phase are the perspective materials for ultrahigh density magnetic recording. The deposition on heated substrate or providing an annealing is required for L10-FePt phase formation. However, heat treatment causes the grains growth and increase of surface roughness of the films, which complicates the practical use of these materials. The introduction of intermediate layers of “third” elements between FePt alloy layers is one of the possible solutions of this problem, which can reduce the temperature of А1‑FePt ® L10‑FePt phase transformation.
Objective. Investigation of the influence of intermediate Ag layer thickness on the structure and magnetic properties of FePt/Ag(7.5; 30 nm)/FePt compositions.
Methods. Film compositions were obtained by magnetron sputtering, structure and properties before and after heat treatment were investigated by X-ray diffraction, atomic force microscopy, magnetometry and resistometry.
Results. It is determined that increasing of Ag layer thickness from 7.5 nm up to 30 nm leads to a reduction of the L10-FePt phase formation temperature for ~ 100 K and to an increase of the compositions coercivity.Conclusions. A possible explanation for the phenomenon of L10-FePt phase formation temperature reduction with increasing Ag intermediate layer thickness lies in the difference between the stress states that occur in these films during annealing due to differences in linear expansion coefficients of their layers. The thickness increase of the intermediate Ag layer increases the composition coercivity as a result of saturation of the grain boundaries of the L10-FePt phase with non-magnetic ingredient and limitation of the exchange interaction between the grains.
I.A. Vladymyrskyi et al., “Influence of the annealing atmosphere on the structural properties of FePt thin films”, J. Appl. Phys., vol. 114, р. 164314, 2013.
M.L. Yan et al., “L10 ordered FePt:C composite films with (001) texture”, Faculty Publications: Mater. Res. Sci. Eng. Center, vol. 19, pp. 2470–2472, 2004.
Y.K. Takahashi et al., “Effect of Cu on the structure and magnetic properties of FePt sputtered film”, J. Magn. Mater., vol. 246, pp. 259–265, 2002.
S. Matsumoto et al., “Magnetic properties of FePt thin films with multilayered structure”, J. Phys.: Conf. Ser., vol. 266, p. 012038, 2011.
J. Ikemoto et al., “Fabrication of ultrathin FePt(Cu) alloy thin films directly on glass disks from Pt(Cu)/Fe bilayers”, J. Appl. Phys., vol. 103, no. 7, p. 7B512, 2008.
Li Zhang et al., “L10-ordered high coercivity (FePt)Ag-C granular thin films for perpendicular recording”, J. Magn. Magn. Mater., vol. 322, pp. 2658–2664, 2010.
K. Dong et al., “Fabrication and magnetic properties of Ag/Fept thin films”, Mater. Manuf. Process, vol. 27, is. 11, pp. 1160–1163, 2012.
J.S. Chen et al., “Where is Ag in FePt-Ag composite films?”, Appl. Phys. Lett., vol. 98, p. 131911, 2011.
I.A. Vladymyrskyi et al., “Influence of intermediate Ag layer on the structure and magnetic properties of Pt/Ag/Fe films”, Vacuum, vol. 101, pp. 33–37, 2014.
I.A. Vladymyrskyi et al., “Influence of the substrate choice on the L10 phase formation on post-annealed Pt/Fe and Pt/Ag/Fe thin films”, J. Appl. Phys., vol. 116, p. 044310, 2014.
C. Feng et al., “Effect of the underlayer (Ag, Ti or Bi) on the magnetic properties of Fe/Pt multilayer films”, Thin Solid Films, vol. 515, pp. 8009–8012, 2007.
F. Wang et al., “FeAu/FePt exchange-spring media fabricated by magnetron sputtering and postannealing”, Appl. Phys. Lett., vol. 95, p. 022516, 2009.
C.Y. You et al., “Particulate structure of FePt thin films enhanced by Au and Ag alloying”, J. Appl. Phys., vol. 100, p. 056105, 2006.
A.-Ch. Sun et al., “Effects of Cr underlayer and Pt buffer layer on the interfacial structure and magnetic characteristics of sputtered FePt films”, J. Magn. Magn., no. 304, pp. 106–110, 2006.
Yi. Peng et al., “L10 FePt-MgO perpendicular thin film deposited by alternating sputtering at elevated temperature”, J. Appl. Phys., vol. 99, p. 8F907, 2006.
LicenseCopyright (c) 2017 NTUU KPI Authors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under CC BY 4.0 that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work