Solid State Communications 150 (2010) 333–336 Contents lists available at ScienceDirect Solid State Communications journal homepage: www.elsevier.com/locate/ssc Ion induced modification in structural and magnetic properties of Pt/Cr/Co multilayers J.K. Tripathi a , A. Gupta b , T. Som a,∗ a Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005, India b UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 017, India article info Article history: Received 20 July 2009 Received in revised form 16 November 2009 Accepted 17 November 2009 by G.E.W. Bauer Available online 22 November 2009 Keywords: A. Pt/Cr/Co multilayer A. PMR media B. Ion irradiation C. Coercivity abstract This paper reports on the change in the magnetic and the structural properties of Pt/Cr/Co multilayers due to 1 MeV N + -ion irradiation at room temperature. We observe irradiation induced formation of the CoCrPt ternary alloy phase at a fluence of 1×10 16 ions cm −2 . Phase formation is accompanied by an enhancement in the coercivity. The enhancement in the coercivity is attributed to inhomogeneous alloying and possible mixing-induced strain. These findings are explained in the light of ion beam induced recoil mixing and ionization events. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction The perpendicular magnetic recording technology provides great advantages for current computer applications and future portable storage devices [1]. Presently, CoCrPt alloy based media are commonplace for perpendicular magnetic recording. It is expected that the current media could theoretically support areal densities up to 500–600 Gbit/in 2 and hence it necessitates looking for the next generation media which will be capable of recording information >Tbit/in 2 . FePt and CoPt alloy based films are such materials which are being considered for extremely high density magnetic recording media in the near future [2–5]. In fact Weller et al. have calculated that these materials have the potential to overcome the superparamagnetic limit [3]. In addition, these materials also show large magnetic anisotropy value which meets the desirable properties for materials to store information up to ∼Tbit/in 2 [3]. However, due to such high anisotropy constants, FePt and CoPt media also have high switching fields which pose difficulties in magnetic switching using industrially viable write ∗ Corresponding author. Tel.: +91 674 2301058; fax: +91 674 2300142. E-mail address: tsom@iopb.res.in (T. Som). head fields [6–8]. Thus, much effort is being put in to overcome the practical challenges associated with reduction of grain size and writing information before their commercialization [7–11]. On the other hand, CoCrPt ternary alloy based media continue to be the present choice because of the reasonably smaller grain sizes (and grain size distribution), low media noise, and good thermal stability than the perpendicular recording media of the past [6]. Usually, CoCrPt ternary alloy thin films are prepared by co- sputtering of elemental targets and/or physical vapor deposition of an alloy target prepared by the solid-state reaction route. The magnetic properties in such films depend on the optimized compositions, grain size and proper texture of the crystal planes to achieve either in-plane or out-of-plane magnetization. Thus, it is essential to understand how to control the global composition and the nature of phase miscibility [12]. Ion beam processing of nanoscale thin film materials offer both, appealing advantages and new challenges in modern science [13]. Besides modifying the magnetic properties, ion irradiation has also been shown to be an efficient tool for patterning magnetic thin films for information storage [14,15]. As far as magnetic multilay- ers are concerned, attention in recent years has been given to ef- fects such as spin orientation transitions from perpendicular to the plane to in-plane under irradiation with light (e.g., He + ) and heavy (e.g., Ar + ) ions [16–18]. Ion irradiation also causes mixing across 0038-1098/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2009.11.028