Evidence for a high T c magnetic amorphous polymorph obtained by swift heavy ion irradiation M. Ghidini a, * , J.P. Nozieres b , F. Bolzoni c , G. Suran b , J.F. Gregg a , B. Gervais d a Clarendon Laboratory, University of Oxford, Parks Road, OXI 3PU, Oxford, UK b Laboratoire L. N eel, Avenue des Martyrs, BP 166 X, 38042, Grenoble Cedex, France c Istituto MASPEC del CNR, via Chiavari 18/A, 43100 Parma, Italy d CIRIL, BP 5133, 14040 Caen Cedex, France Abstract The intermetallic compound CeCo 3 has been irradiated at GANIL by 1 GeV 208 Pb ion beams. The irradiated samples are found to be strongly amorphised. A track diameter of 8 nm is found. The magnetic properties of the ir- radiation induced CeCo 3 amorphous phase have been studied in detail and found substantially dierent with respect to those of amorphous CeCo 3 obtained by conventional methods. In particular, an increase of about 200 K in the Curie temperature is observed, suggesting that a dierent type of chemical short range order might have been stabilized by irradiation. Ó 1998 Elsevier Science B.V. All rights reserved. PACS: 75.70.Cn; 73.23.b Keywords: Latent tracks; Amorphous magnetism; Thermal spike 1. Introduction Amorphous metals and alloys can be obtained by rapid cooling either from the liquid or the vapour phase by dierent techniques [1,2]. It is well-known that amorphous samples produced by dierent methods can show dierent properties. This is generally ascribed to dierent degrees of structural relaxation, resulting from dierent amounts of strain frozen in the samples during the rapid cooling process. However, such dierences are normally quite small [3,4]. In a few cases, for a given composition, substantial dierences in the magnetic properties have been observed in alloys prepared with strongly dierent quenching rates [3,5]. Detailed studies have shown that this was due to two dierent types of Chemical Short Range Order (CSRO) (amorphous polymorphism) [6]. CeCo 3 is a metallic ferromagnet [7]. As 3d- magnetism of cobalt is normally more robust in the amorphous state than in the crystalline state [3], a spontaneous magnetic moment of about 0:2 l B =f :u: and a Curie temperature T c  of 80 K are reported for crystalline CeCo 3 [8], while a Nuclear Instruments and Methods in Physics Research B 146 (1998) 260±264 * Corresponding author. Address: Dip.to di Fisica, Univer- sita' di Parma, v.le delle Scienze, 43100 Parma Italy. Tel.: +39 521 90521; fax: +39 521 905223; e-mail: Ghidini@®s.unipr.it 0168-583X/98/$ ± see front matter Ó 1998 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 8 ) 0 0 4 9 1 - 1