Europhys. Lett.
Volume 64, Number 5, December 2003
Page(s) 668 - 674
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00279-7
Europhys. Lett., 64 (5) , pp. 668-674 (2003)

Xenon-ion-induced phase transition in thin $\chem{Co}$ films

K. Zhang1, R. Gupta1, 2, K. P. Lieb1, Y. Luo3, G. A. Müller1, P. Schaaf1 and M. Uhrmacher1

1  II. Physikalisches Institut and SFB 602, Universität Göttingen Tammannstr. 1, D-37077 Göttingen, Germany
2  Institute of Instrumentation, D. A. University - Khandwa Road, Indore-452017, India
3  I. Physikalisches Institut, Universität Göttingen Tammannstr. 1, D-37077 Göttingen, Germany

(Received 26 May 2003; accepted in final form 30 September 2003)

We report on the observation of the ion-induced hcp $\rightarrow$ fcc phase transition in 75 $\un{nm}$ thick polycrystalline $\chem{Co}$ films, which were irradiated with 200 $\un{keV}$ $\chem{Xe}$ ions to fluences of $2.5\times 10^{13}$- $8\times
10^{15}$ $\un{ions/cm^2}$ at a temperature of 300 $\un{K}$. Analyses by means of Rutherford Backscattering Spectroscopy (RBS), X-Ray Diffraction (XRD), Magneto-Optical Kerr Effect (MOKE) and Vibrating Sample Magnetometry (VSM) provided information on the film thickness and the implanted $\chem{Xe}$ profiles, the phase structure, the ion-induced lattice expansion and the magnetic hysteresis, respectively. After film deposition and irradiations up to $4\times 10^{14}$ $\un{ions/cm^2}$, we predominantly found the hcp phase (XRD, uniaxial MOKE pattern) with an in-plane magnetization. The transition to fourfold in-plane magnetization typical of the fcc-phase occurred around a fluence of $2\times
10^{15}$ $\un{ions/cm^2}$. We interpreted these findings as due to rapid cooling of thermal spikes into the metastable $\chem{Co}$-fcc phase.

61.80.Jh - Ion radiation effects.
75.30.Gw - Magnetic anisotropy.
75.50.Cc - Other ferromagnetic metals and alloys.

© EDP Sciences 2003