Formation of unusual intermetallic phases by vacuum PLD A. Gorbunov a,* , A.A. Levin a , A. Mensch a , D.C. Meyer a , A. Tselev a , P. Paufler a , W. Pompe a , D. Eckert b a Dresden University of Technology, TU Dresden, D-01062 Dresden, Germany b Institute for Solid State and Materials Research (IFW), D-01171 Dresden, Germany Abstract Unusual phase formation in Fe–Cr alloys co-deposited by pulsed laser deposition (PLD) is reported. Contrary to expectations to obtain a continuous series of supersaturated body centered cubic (b.c.c.) solid solutions, the structure of alloys develops from a tetragonally distorted b.c.c. at low Cr-content to an ordered primitive orthorhombic crystal structure of the A15 type at nearly equiatomic composition. It seems to be the first observation of an ordering of restrictedly soluble components under the bombardment of hyperthermal species in PLD. The film formation in PLD can be described in the frames of subplantation model of Lifshitz et al. where the phase that forms is a product of kinetic factors like defect formation beneath the free surface and their disintegration rather than thermodynamic driving forces. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Pulsed laser deposition; Hyperthermal species; Metal thin films; Intermetallic phases; Implantation; Metastable phases 1. Introduction Interesting para-ferromagnetic transformations induced by heat treatment of the pulsed laser deposited (PLD) Fe 100x Cr x alloys has been reported recently [1–3]. Initially paramagnetic (PM) at room tempera- ture, the Fe-rich Fe–Cr thin film alloys become ferro- magnetic (FM) after local or global annealing at a temperature above 500 8C. This transformation has been ascribed to thermally induced growth of Fe-rich magnetic nanoclusters [2] or to the rapid quenching of the melt with the formation of an undercooled FM body centered cubic (b.c.c.) solid solution [3]. How- ever, the nature of the initial PM state of the alloys remained open. Although the Fe–Cr materials system has a miscibility gap, a continuous series of b.c.c. a- (Fe, Cr)-like solid solutions can be stabilized at room temperature by a rapid cooling the alloys from above 830 8C. These undercooled b.c.c. alloys become PM at room temperature when they bear more than 70 at.% Cr [4] which is in contradiction with the results of Refs. [1–3]. Structural investigations reported in the present paper yield that instead of the expected for- mation of undercooled b.c.c. Fe–Cr solid solutions there form unusual for this materials system meta- stable intermetallic phases. The formation of ordered metastable phases by energetic deposition is a rather seldom phenomenon and to our knowledge is reported for the first times for PLD. 2. Experimental Fe–Cr is a materials system with a slightly positive mixing energy of þ0.25 eV/atom (at 1100 8C) and Applied Surface Science 197–198 (2002) 475–480 * Corresponding author. Tel.: þ49-351-463-31450; fax: þ49-351-463-31422. E-mail address: gorbunov@tmfs.mpgfk.tu-dresden.de (A. Gorbunov). 0169-4332/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0169-4332(02)00374-4